I have a question about the great time war

So, my friend's the one who got me into Doctor Who. I watch the modern episodes and he watches the newer ones. (He hasn't seen a single new episode, and i've only seen part one of Arc In Space) So, since he knows more about DW than I do, I asked him about the time war, and how all of the Timelords died, because, they just talk about it without any details. He had no idea what I was talking about. Does this get explained later? He really only watches 4th, but he watches other ones, too. I don't want to have it spoiled if it's something that gets explained later, but if it's an older episode, then I want to know what's going on. Thanks.