One of the acid tests of mastering a foreign language is your level of understanding of local slang. In most cases, especially if learning through traditional classroom methods, slang tends to be absorbed after formal language.
And yet, it is often the most interesting part. One of my favourite street expressions in Brazilian Portuguese, is "tá ligado?".
It is in fact a contraction of "você esta ligado?" which literally means "Are you switched on?" which in turn means "Do you understand?" or " Are you listening?"
It's roughly equivalent do the slang phrase "know what I mean?" in the UK or perhaps even the famous "innit?" and like its English counterparts it's best said not written.
"Tá ligado", often overused in Hip Hop circles