The Doctor wasn't certain he should go into complete detail--a great deal of what he and Martha had been through was rather unpleasant, particularly for her--so he didn't. Oh, he still told her about finding Jack, and traveling to the end of the universe, but he glossed over the bits with the Master, telling her only that they had worked together to overthrow his old friend and enemy when he used his position as Prime Minister of England to take over the world. He then went on to describe how she'd decided on her own to leave, giving him rather a good lecture about not noticing her by way of telling him about a friend of hers. Then, he told her how he'd first met Donna, and then found her again, and gave Martha a few highlights of his journeys with his best friend.
"We eventually managed to track Earth down again and found out there was a bit of problem with Daleks again, you remember the Daleks. Rose was able to punch through the walls of the dimensions since the Dalek's had compromised their integrity and, well, it gets a bit complicated, but we sort of wound up with a second me, so when everything was sorted again, he went home with Rose after I dropped everyone off, and I've been on my own since."
He hoped she didn't notice how much he'd left out. He was willing to be honest with her, but only to a point. Certain things were still extremely uncomfortable to think about, let alone mention.