A phrasal verb consists of a verb and a preposition or adverb that modifies or changes the meaning ; 'give up' is a phrasal verb that means 'stop doing' something, which is very different from 'give'. The word or words that modify a verb called particle. They are widely used in both written and spoken English, and new ones are formed all the time as they are a flexible way of creating new terms.
Examples : act up (no object): misbehave (for people); not work properly (for machines). "The babysitter had a difficult time. The children acted up all evening.“ "I guess I'd better take my car to the garage. It's been acting up lately."
act like (inseparable): behave in a way that's like _____ . "What's wrong with Bob? He's acting like an idiot." Note: This phrasal verb is very informal. "His theory seems, at first, to be plausible, but the facts in his research don't add up ." add up (2. separable): find the total. "What's the total of those bills? Could you add them up and see?“ add up to (inseparable): to total. "The bills add up to $734.96. That's more than I expected!"
An idiom is a group of words with the meaning of the individual words are different from the meaning of the whole phrase. Examples: bad-mouth: say unkind, unflattering, embarrassing (and probably untrue) things about someone. A: "I don't believe what Bob said. Why is he bad-mouthing me?“ B: "He's probably jealous of your success."
be a piece of cake: be very easy. A: "Bob said the test was difficult, but I thought it was a piece of cake .“ be all ears: be eager to hear what someone has to say. A: "I just got an e-mail message from our old friend Sally." B: "Tell me what she said. I' m all ears !"