what is difference between conjuction and preposition?
The difference between the both can be well understood by their explanation:
Preposition: It is a word which expresses the relation of a noun or pronoun with the other words in the sentence. For instance, in the library, on the table, etc.
Conjunction: It is the part of speech which helps to connect words, phrases, clauses or sentences. For instance, and, but, because, etc.
Some prepositions can act as conjunctions but all conjunctions cannot be prepositions.