parts of speech

An adverb is a word that describes a verb, and adjective, or another adverb.

A preposition is a person, place, thing or idea.  

Adverbial phrases describe action. 

A verb is a word in the predicate that tells physical or mental action or a state of being. 

Adverbs can be used to make comparisons.

If the subject is singular, the verb can be plural.

I kicked the ball between the goalposts. (Goalposts is a preposition.)

Dad works hard to make the lawn look nice.  (Hard is an example of an adverb.)

The pirates buried their treasure under a tree.  (Under is a preposition.)

A prepositional phrase can act as an adjective or an adverb.