In English we toss around phrases like nowhere to go, where from?, where to? In Portuguese it's a little different. For the most part, onde does all the heavy lifting. But, it's important to use it with the right prepositions and verbs to get the meaning right.
Onde in Portuguese is used in a variety of ways. Often with creativity, often confusing.
You can also say, "Onde fica?" (more about this)
Literally: "Of where you are?"
A = to, and onde = where. A+onde = aonde (to where)
Brazilians will combine the "onde ir" so that it sounds like, "onjee-r"