Learn Finnish: Selitä minulle, mikä vika tässä on. - Explain to me what the fault is here.

No, and that is the best part about indirect questions in Finnish! Unlike English, which flips words around (direct: "what is the fault?", indirect: "what the fault is"), Finnish keeps the exact same word order. A direct question would be Mikä vika tässä on? (What is the fault here?), and it stays exactly the same when attached to the main clause.

The translation says "here", but doesn't tässä mean "in this"? Why not use täällä?

In English we often say "what is wrong here", but in Finnish, when you are talking about a specific object, device, or situation right in front of you, you use tässä (in this). The word täällä refers to a broader physical location, like being "here" in a room or a city.

Does mikä vika literally translate to "what fault"?

Yes! While the natural English translation says "what the fault is", the Finnish phrase directly pairs the question word mikä (what) with the noun vika (fault, defect, or flaw). You can think of the whole clause literally as "what fault is in this".

Is selitä a command? Why does it only have one 't' when the dictionary form is selittää?