With Bitcoin, the Segregated Witness (SegWit) process separates (or segregates) two elements of the transaction so that block capacity is increased.
Segregated Witness is a process where transaction signatures are detached from bitcoin transactions. This allows a greater number of transactions to be included in each block.
Segregated Witness is an upgrade to the protocol that also helps protect against transaction malleability. The witness portion contains information needed to check that the transaction is valid.