Learn Turkish: Bu bir ev. - This is a house.

You would ask Bu ne? (What is this?). To form the answer, you simply replace the question word ne (what) with the actual object to get Bu bir ev.

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

Turkish doesn't use a separate word for "is" in simple descriptive sentences. Just putting bu (this) and bir ev (a house) together naturally creates the meaning "This is a house".

Why is the word bir placed in the middle?

The word bir means "a" or "an", and it goes directly before the noun it describes (ev). The word bu is the subject ("this"), so it comes first.

What happens if I leave out bir and just say Bu ev?

If you say Bu ev, the meaning changes from "This is a house" to "This house". You would then need to add more information to finish the sentence, for example: Bu ev büyük (This house is big).