SegWit refers to process changes made in Bitcoin regarding storage of transaction data by increasing the Block size, it was accomplished by removing signature data from bitcoin transactions. When certain parts of a transaction are removed, it frees up space or capacity to add more transactions to the chain.

It went live in August 2017 after being released in 2015. It also helped to fix tampering in Bitcoin transaction ids, that was possible earlier. SegWit2X was a proposal to increase Bitcoin’s block size from 1 MB to 2MB. SegWit2X developers wanted to hard fork the Bitcoin to carry out these changes but abandoned it, owing to lack of consensus.