But, then I read somewhere that we do use 100% of our brain but only like 10% at one time since our brain is like a database or computer. I mean a computer doesn't use all of it's memory at once or it will crash but you still use 100% of the computer. I wish I could remember where I read that. I hope I explained that correctly. If I'm wrong, point it out. Thanks.
That sounds right. When we perform a certain mental or physical task, the related part of the brain heats up. We can see this in real-time MRI scans. In order to light up the whole brain at once, you would have to be thinking about several things at once while performing multiple physical tasks, to a degree that probably is impossible.
One possible origin for this myth, by the way, is that about 1/10th of our brain is actually gray matter, i.e., "the stuff that thinks". The rest is white matter. The white cells interconnect different regions of the brain, like the system bus in your computer. So a reporter in the early 20th century who learned this wrote misleadingly that only 10% of our brain is used. In a way it's true, but not in the sense that parts of our brain are permanently latent and waiting to be discovered.