Harry Potter -- I need help.

I just finished reading the Harry Potter series again. (It's amazing -- still.) (Oh, and spoiler alert.) But I was at the the part in the Deathly Hallows where Harry is talking to Dumbledore in King's Cross station, and I realized that I had no idea what Dumbledore meant when he was explaining Harry and Voldemort's connection for the umpteeth time. I had something to do with Harry's blood, and Lily's love, and Voldemort's... um... yeah, Voldemort. I'm on the brink of understanding it, but I just can't get it. I was wondering if anyone could explain this a little better so I could understand...? Thank you. :)