Here's Rucknium's latest article about the infamous #monero 18-block reorg: What happened, why it matters, and what it has to do with the annoying 10 block lock.

If I could understand the whole thing enough to be able to do the diagrams, you can do it as well!

But seriously, give it a read. It's important if you care about (and want to understand) Monero's inner workings and quirks better: