About Atharv Ved
The last of the four Ved, the Atharv Ved ("Wisdom of the Atharvan Priests", the Book of the Spell), is completely different from the other three Ved and is next in importance to Rig Ved with regard to history and sociology. Atharv means the stationary. The Atharv is Prajaapati, the god who has given the fire to the mankind. The Atharv Ved takes its name from one of the Braahman families traditionally believed to have composed the Ved. Like the Rig Ved, it is a collection of entire hymns. The hymns of The Atharv Ved, however, are of a more diverse character than the Rig Ved and are also simpler in language.

Atharv Ved is the  Kriyaa (action) part of the Ved. Mostly meant for the worldly knowledge, it is an essential part of education for those who aspire to be the preceptors, also called Aangiras, Atharv Aangiras, Bhrigu Aangiras, Kshatra (one who acts) or Bhaishajya . The verses of Atharv Ved are called Siddh Mantra. It deals with diseases and their cure, rites for long life, rites for fulfilling other desires, construction of buildings, commerce and trade, administration etc.

There are 6,077 Mantra in ths Ved spread over 20 Kaand and 4 Prapaatak.
There are no Aaranyak for this Ved and there is only one Braahmana - the Gopath Braahman.
The Prashnopanishad, Mundak Upanishad and Maandookya Upanishad belong to this Ved.

Many people think that at first the whole Ved was divided into 3 parts, and Atharv Ved is a later addition, but it is not so - Brihadaaranyak Upanishad (2.4.10), Mundak Upanishad (1.1.5), Mahaabhaarat, Vishnu Puraan and Patanjali in his Mahaa Bhaashya, in his commentary on Rig Ved verse 4.48.6, - all support 4 Ved from the beginning. Major Upanishad - Mundak, Maandookya and Prashn etc Upanishad, belong to Atharv Ved. If you read somewhere that "Ved are three" - it means that there are only three types of Mantra - Rig, Yaju, and Saam. Atharv Ved refers to three types of Mantra in 10.7.14. Most of the Mantra in Atharv Ved are classified as Rig because they are metrical.

They include almost exclusively of a wide variety of hymns, magical incantations, and magical spells. It contains spells for everything from success in love to the realization of other worldly ambitions prevalent at its time. Largely for personal, domestic use, it was not originally accepted as authoritative because of the deviant nature of its contents. Scholars believe that it dates from a later time .Eventually it was acknowledged as one of the four Ved, especially after its adoption as a ritual handbook by the Braahman.

Shiv's Sharabh Avataar, who pacified Narasinh Bhagavaan after being angry on Hiranyakashyap, is mentioned in Atharv Ved.

Atharv Ved calls itself by other names such as Brahm Ved (Atharv Ved, 15.6.8); Atharv Angeeras Ved (Atharv Ved, 10.7.20); and Ved of Healing or Bhaishajya Ved (Atharv Ved, 11.6.14). Shatapath Braahman calls it as the Kshatra Ved (the Ved dealing with polity and governance of society (Atharv Ved, 14.8.14), and also as Angiro Ved (13.4.3). It is because that Atharv Ved has a large number of Hymns on these topics.

Are There Any Parishisht in Atharv Ved
(1) Atharv Ved has 5 Atharv Sheersh and are known as "Atharv Sheersh" - they are not generally called or known as Parishisht.
(2) Atharv Ved does have Parishisht and this text with the name "Atharv Ved Parishisht" got published by Chaukhamba Orientalia in 2008.

Does Atharv Ved use Caste System? specifically is the Shoodra or laboring class mentioned?"
The word Shoodra or its equivalent does not occur in the Atharv Ved. The "Vish" means all persons and workers which includes - traders, merchants (Vanij), chariot makes (Rathakaar), smiths (Karmaar), agricultural workers who operate the implements like plow, yoke (see the Hymn 3.17.1) and the workers who build houses (3.12). Thus "Vish" was later subdivided into Vaishya and Shoodra. Even in the times of Bhagavad Geetaa, Vaishya included both traders, agriculture workers and artisan; and all the unskilled labor was classified as Shoodra.

The Yajur Ved prayer (Shukla Yajur Ved, Vaajsaneyee Sanhitaa, 18.48) shows an equal attitude to all the four types of workers - "Give luster to our Braahman, Give luster to our kingly men, Give luster to our Vaishya and Shoodra". The luster is physical, psychological and intellectual.

Some orthodox people say that a Shoodra is not fit to hear the Ved. There is no support for such a statement in the Ved; on the contrary Shukla Yajur Ved 26.2 explicitly states - "May I speak the sacred word to the masses of the people - to the Braahman, Raajanya (Kshatriya), to the Shoodra and Vaishya, and to our own men and the strangers." Note that Shoodra takes priority over Vaishya, and the word strangers.

Some teacher wants to spread wisdom to masses - no attempt at keeping the people ignorant - See Atharv Ved, Hymn - 6.69
Ashwins, Lord of Light, fill me with the sweetness of the bee honey,
So may I speak the glorious word to the masses of the people.

Devtaa in Atharv Ved
(1) Agni, (2) Bhoomi Sookt (entire 12.1 hymn - 63 verses), (3) Chandra (4) Indra, (5) Mitra, (6) Soorya (7) Varun

Education in Atharv Ved
There are 10 hymns in Atharv Ved on this topic. Usually Brahmcharya is trandlated as "celibacy" but its literal meaning is "to move in Brahm", or "to move the supreme state of consciousness named Brahm". Thy Hymn 11.5 is the earliest attempt to describe the process of Deekshaa (initiation). Another Hymn 6.133 describes the importance of Mekhalaa.

Health, Bliss and Aayur Ved in Atharv Ved
There are 213 hymns in this category. The sages of Atharv Ved did not define health as mere absence of disease or define a million diseases with an associated herb or pills for curing them. First they asked the question "why to live long?" and answered it in (19.69) - "For a hundred years may we see, For a hundred years may we live, For a hundred years may we know, For a hundred years may we rise, For a hundred years may we ..."

Hospitality in Ved
Hospitality was the characteristic of Vaidik life, especially the wandering ascetic (Pravraajak) was highly respected. He was called Vritya.

Kaal in Ved
There are about 6 Sookt dealing with Kaal or Time. The sages knew the distinction between the methods of marking time and abstract concept of Time itself. the seasons mark the passage of Time. But the Atharv sages declare in the Hymns 19.53 and 19.54 that Time is an abstract entity which causes all the dynamics seen in the Universe. The verse 19.53.6 declares that Time created Earth, the Sun burns in Time, and all existences are defined in Time. The verse 19.53.7 declares that the concept of Mind exists in Time only, because we know the mind by the changes in our thoughts etc and all changing entities exist in Time only.