On 08/01 there will be a hard fork creating a second blockchain (Bitcoin Cash, BCH). All coins which are on the BTC blockchain before the fork will be copied onto the BCH blockchain. This means: For every BTC you have, you will get one BCH.
To have access to your BCH, move your BTC BEFORE 08/01 (!) to a wallet of which you and only you control the private keys (because they are the keys to BOTH your BTC and your BCH). Otherwise you are missing out on your BCH (which will be received by the actual owner of the private keys) and therefore you will lose money. After the fork you can use custom software to spend your BCH. Or you can trade them on some (not all!) exchanges like kraken for money or BTC.
(or just hodl them and see how the price behaves)
BCH will have a certain value (futures are currently selling for $350). This value will not be created out of nowhere, but instead this value will be moved away from the original BTC value. So IN THEORY (this is not an actual price prediction since there are lots of other, mostly psychlogical factors involved) the BTC price prefork will be the same as the sum of the BCH + BTC price postfork.
Maybe you remember the talk about that user activated soft fork (UASF: BIP-148) which would have taken place on 08/01. This is no longer a problem, because BIP-148 nodes will do nothing but reject all blocks which do not signal SegWit. Due to BIP-91, currently all blocks are signaling SegWit so there will be no unexpected behaviour.
Coinbase locked an account of mine with .2ish bitcoin in it. What will most likely happen to this bitcoin?