Essentially they plan to split the bitcoin currency into a new bitcoin coin called Bitcoin Gold so mining is less centralized. Then there's another fork is November and it just turns into a big headache. You can google it a bit for a more in depth answer
The fork has caused btc price to spike cuz last fork in August which created bitcoin cash, everyone who had bitcoin got an equal amount of bitcoin cash. So if I had five bitcoin on an exchange, I automatically received five bitcoin cash coins. I, and most people just sold these right away into bitcoin and we're essentially given free money. In my case, I sold at $900 a coin the day I got it. It peaked at $1100, crashed, and is sitting at about $300ish ATM.
So now people are loading up on bitcoin hoping they get free bitcoin gold they can flip for free money again. That is also why Alts have been in the shitter the past month. Right around fork time alts should receive a pimp and we should see btc dip a bit and then re establish a new, higher low.