A preposition is a word we use in front of a noun or pronoun to form a phrase. Prepositions can describe the position of something, e.g. on the table, or when something happens, e.g. in summer. There are two types: simple prepositions, such as to, along and complex prepositions, i.e. two-word combinations, such as along with, because of, due to, or three-word combinations, which usually take the format of simple preposition + noun + simple preposition, as in, well, in front of or in accordance with.
Most students complain that the use of prepostions is very difficult in English, but in fact use of prepositions is difficult in any foreign language as certain prepositions are used after particular adjectives or verbs, etc.