Im not a 100% expert on the matter, but from my knowledge, a Bitcoin is an encrypted currency (meaning payments are anonymous) that you acquire from either buying one (prices change rapidly, but they're over $10,000 right now, so buying one isn't likely) or bitcoin mining. Bitcoin mining is essentially where a mining software uses your CPU to do complex math problems, which takes up a lot of power, to get a bitcoin. It's way harder than it looks because it REALLY takes a lot of CPU to do it. From my knowledge, the only reason why it's really hard is simply because it's expensive.