Verbal Lego blocks: Just as you combine Lego pieces to create something new, phrasal verbs combine a verb with other words to make a new meaning. (preposition or adverb)
The meaning changes: Often, you can't guess the meaning of a phrasal verb by looking at its parts. For example, "give up" doesn't mean to "give" something in an upward direction - it means to stop trying or surrender.
They're very common in everyday speech: Native English speakers use phrasal verbs all the time, often without realizing it.
Examples:
"Turn off" (the lights) = to switch something to an inactive state