Phrasal verbs are a combination of a verb and one or more particles, like adverbs or prepositions. They have a different meaning than the individual words used alone. For example, "go on" means to continue, not just to go. They are commonly used in spoken and informal English. It's important to learn them because they are used frequently in everyday conversation. To use them effectively, it's helpful to memorize their meanings and practice using them in context, as their meanings can sometimes be idiomatic.