To summarize:
There will most likely be a hard fork on August 1st at 12:15 UTC. Similar to ETH and ETC, if a certain amount of Bitcoin miners transfer over to this new , to generalize things, system , it would mean that we would now have two branches of the same coin, so now we will have BTC and BTC Cash. Now, if your money is on an exchange that has not put into place a plan to support the new currency BTC C, you are losing out on a huge potential, because you are entitiled to a 1 1 ratio of BTC to BTC C. What may happen with BTC C and the price of bitcoin is uncertain, it may turn out the BTC C has a very small value and the effects are minimal on BTC, it could turn into literally free money with no effect on BTC, it could create a market where you will need both sets of currency to represent what use to be a BTC because lets say 50 percent drop in BTC and 50 percent of BTC value is put into BTC C, or shit all could happen and BTC C will be entirely worthless.
NOW, the big thing to realize is that you have to make sure you are going to get the money your entitled to , the BTC C when the fork happens (it looks like it will happen). If your money is on coinbase or a lot of other online exchanges, THEY WILL TAKE YOUR BTC C for ALL THE BTC IN YOUR WALLET FOR THEMSELVES. That is why it is recommened to put your BTC on a private wallet with your keys, OR get on an exchange that is doing a 1 for 1, basically giving you your BTC C for the equivalent amount of BTC like BITTREX.
Now theres three angles to consider in next 48 hours. Altcoin market (if your invested), bitcoin market, and the BTC C market. You should keep an eye out on all three (two if your not playing alt coins other than BTC) and ensure that if theres some huge market event you dont fuck up just because you werent paying attention.