Phrasal Verb is a group of words which have a verb & a adverb or preposition.

Features:

1. The words that are used in phrasal verbs act together.
2. They form a  new single verb.
3. They have a new meaning which is different from the meaning of the individual words.

Examples:

1. He broke the window.
2. Our car broke down on the highway. 

In the first example, the verb 'broke' means damaged.  

In the second example, the phrasal verb 'broke down' means the car is not moving now and needs repair.

It is combination of broke (verb) + down (preposition). 

Some more Examples:

1. Please take off your shoes.
2. Children, come back for the next game.
3. Sam gave up all hopes to recover.