Learn German: Braucht ihr das Geld? - Do you all need the money?

The verb ending must match the subject, which here is ihr (you all). For regular verbs like brauchen (to need), you find the stem by dropping the -en and then add a -t when used with ihr.

Who exactly is ihr referring to?

ihr is the plural informal version of you, similar to saying you all or you guys. You use it when speaking directly to two or more people whom you would individually call du.

Where is the word for do in the German sentence?

German does not use helper words like do or does to ask questions. Instead, you simply move the main verb to the very front of the sentence. Literally, this asks: Need you all the money?

Why do we use das for the money?

Geld is a neuter noun, so its word for the is das. In this sentence, das Geld is the direct object (the thing being needed), but the neuter article das conveniently looks exactly the same whether it is the subject or the object!