"I run home."
Domus (here domum) is one of the lucky nouns that has the locative. Nouns with the locative lose the preposition for place from where and place to where (which is used here) constructions.
Place to where : Domum curro -> "I run home" vs. Ad villam curro -> "I run to the house".
Place from where : Domo curro -> "I run from home" vs. A villa curro -> "I run from the house".
Place where (the locative is used for domus) : Domi curro -> "I run at home" vs. In villa curro -> "I run in the house".
Thank you. I would give you ten lingots if it allowed me to. I have been told to just to think about the five cases to begin with but I am getting an idea of what locative must be. I am pretty much just relying on my understanding of German and Spanish at this point. It looks like they have included a good mix of cases in these early lessons.
No worries, I will link a video that someone posted in another discussion. It talks more about the locative (when to use it, how to form it, shows some examples). It's not very long but it may help with getting more familiar with it: https://www.youtube.com/watch?v=VwLS-fh3pVg