We need to understand few terms before stepping into SegWit2x
Also coined as UAHF (User Activated Hard Fork), splits the chain into two. All the blockchain data available till the block where the split happens will act as the base data for the new chain.
This is the reason if you are the holder of Bitcoins before August 1, you can have the same amount of Bitcoin cash.
Also known as UASF, is a temporary split in the blockchain due to a network issue, or an upgrade plan that is backward compatible.
What is SegWit?
Segregated Witness aka SegWit is a soft fork that enhances the use of 1 MB block size limit efficiently so that more transactions could fit-in.
Usually, a block consists of both transaction data and signatures to verify. The signature takes more than 50% space that of transactions. With the SegWit implementation, the block contains only the transaction data. The signature data would be maintained separately.
The network nodes that adapts to SegWit can verify the block alongside the nodes which do not adopt the SegWit. And these old nodes can still verify transactions without the signatures. This way the network keeps alive without any glitches.
SegWit is successfully activated on August 24 as Bitcoin improvement proposal (BIP) 141.
What is SegWit2x?
The SegWit2x is a hard fork implementation that leverages on SegWit for changing the block size permanently, and the plan is to implement in the November 2017. Which is also known as Bitcoin improvement proposal (BIP) 148.
Each block would have 2MB transaction capacity. And 8MB total block size including the signatures.
The Bitcoin community which consists of developers, miners, exchanges, merchants, and users is having a lot of disagreements over the adoption of SegWit2x. Few community leaders are predicting that the Bitcoin could split up leading to the creation of a new Cryptocurrency.
When a hard fork or a soft fork is about to happen, it is always recommended to have the Bitcoins in cold storage.