They are a group of 2 -3 words put together to mean specific actions. Phrasal Verbs are made of a verb and a participle, normally a Preposition and sometimes an Adverb. We use these these verbs the same ways as other verbs although the structuring of the phrase can change. There are two types of phrasal verbs, Transitive and Intransitive, or Separable and Inseparable.
The phrasal verb itself has a totally different meaning than the verb inside the phrase. Normally a phrasal verb can have two different meanings or more depending on the context.