Trying to load from uSD card, stuck on 3 solid lights

I downloaded the latest Debian image. Decompressed it, and flashed it onto an uSD card. When I plug it into the BBB and connect the USB power, the first three lights come on and stay on forever. What does this indicate?

TLDR, 3 solid lights when booting from uSD, whats the problem?

It didn't like what it saw..

1: which debian version?
2: does it boot if you hold down the "boot" button