In a sentence words are divided into different classes or kinds because of their functions and usage. And it is described by the term of parts of speech.
বাক্যে ব্যবহ্রত প্রত্যকটি অর্থবোধক শব্দকে parts of speech বলে।
Parts of speech help to understand the uses or functions of words and how different words can make a meaningful sentence.
There are eight types of part of speech.
Collected from: http://www.english-bangla.com/grammar
Noun
Pronoun
Verb
Adverb
Adjective
Preposition
Conjunction
Interjection