Parts of Speech

In grammar, a part of speech or also known as a word class, a lexical class, or a lexical category is a linguistic category of words or more precisely lexical items, which is generally defined by thesyntactic or morphological behaviour of the lexical item in question. Common linguistic categories include noun and verb, among others. There are open word classes, which constantly acquire new members, and closed word classes, which acquire new members infrequently if at all.
Traditional grammar classifies words based on eight parts of speech: the verb, the noun, the pronoun, the adjective, the adverb, the preposition, the conjunction, and the interjection. Each part of speech explains not what the word is, but how the word is used. In fact, the same word can be a noun in one sentence and a verb or adjective in the next.
This is summary of the 8 parts of speech:
1. Verb 
Function: Action or state
2. Noun
Function: Thing or person
3. Adjective
Function: Describe a noun
4. Adverb
Function: Describe a verb
5. Pronoun
Function replaces a noun
6. Preposition
Function: Links a noun to another word
7. Conjunction
Function: Joins clauses or sentences words
8. Interjection
Function: Short exclamation, sometimes inserted into a sentence

source: englishclub