What is adjective, adverb, preposition and conjunction?

An adjective is a describing word, for example: Those colors are very bright.
Bright is the adjective, because its talking about the colors.

An adverb is a word or phrase that modifies the meaning of an adjective, verb, or other adverb, place, or time. For example:  She kindly told told him to go away. Kindly is the adverb.

A preposition is a word that tells you where something is, for example: The puppy is on the floor. ON is the preposition.

Lastly, conjunctions are joining words, like: and, or but.

Hope it helps :)

 An adjective is a word or phrase that describes a noun

An adverb is a word or phrase that modifies another word

A preposition is a word governing a noun/ pronoun

And a conjunction is a word used to connect thoughts smoothly

He discusses the problem of human destruction of nature and gives solution to prevent it.