Phrasal verbs 6 - up/down

Why do you need to know when to use 'up' or 'down' as part of a phrasal verb? And what IS a phrasal verb?Up and down are often used with a verb. To sound more like a native speaker, it is useful to know some of the times when this is so!And a phrasal verb is a combination of two or three words that have a special meaning when used together. They consist of a verb and a preposition.