Learn Swedish: Vad kostar den här tröjan? - What does this sweater cost?

In Swedish, when you use den här or det här (this), the noun that follows must be in the definite form (the "the" form). So you literally say "this here the sweater": den här tröjan.

How do I know to use den här instead of det här?

It depends on the noun. Because sweater is an en-word (en tröja), we use den här. If we were talking about an ett-word like an apple (ett äpple), we would use det här (det här äpplet).

Where is the word for "does" in this sentence?

Swedish doesn't use helper words like "do" or "does" to ask questions. Instead, you just put the main verb right after the question word. So Vad kostar... literally translates to "What costs...".

Does the word här literally mean "here"?

Yes! To say "this" in Swedish, you literally say "it here" (den här). It points to a specific thing that is physically close to you.