Spanish syntax really tries to help you, sometimes more than the DuoLingo interface does. Here, the "Te" is a a huge signpost alerting you to the fact that what is coming in likely to be reflexive. The conjugation of the verb confirms it (eg., Te + -iste is like a double "you"). In this case, the root is irse, not ir. The second huge clue is that the preposition is de and not a. So if you learn to look for the patterns ir a and irse de you will catch the difference between go to and left from (or went from).
So irse means to leave. It's a reflexive version of ir. So that would translate to me voy, te vas, se va, nos vamos, se van. Basically, I leave, you leave, he/she leaves, we leave, they leave. The me/te/se/nos are reflexive pronouns and therefore always take the form me, te, se, nos. In this case it's "you left your house" So it's Te (the reflexive pronoun) fuiste (2nd person preterite of ir) de tu casa. Te is always an object pronoun or reflexive pronoun.
Te fuiste de - means you went -Even when you hold your mouse over the word it shows the words was , were, went. They don't even mention ( left ) in the list. Now correct me if I'm wrong and I'm not! How is someone who is learning going to know what the hey..... If you mean left PUT IT IN the list...