Probably one of the most common phrases in Brazilian Portuguese, it means, 'How have you been?' But how does this work? ANDAR in Portuguese is one of those verbs that can simplify the language. We all know that Como você está? or, Como você vai? are the proper ways to ask how are you? -- CORRETO.
But Brazilians will also use the verb ANDAR (to walk, to go around, roam) here to express been.
ANDAR in Portuguese
You can think of this as been going around -- which makes sense since ANDAR has the meaning of going, going around (wandering).
The reason for this use of ANDAR is pretty simple: It's easier to say for example, eu ando preocupado than it is to say, eu tenho andado preocupado (I've been worried). Portuguese is a complicated language and in general, Brazilian seek out shortcuts to simplify when possible.
You can of course get real fancy with this one and use it complex tenses like:
You will also hear people saying, Como tu andas?. This is an even less formal method, utilizing the tu form.