Sagwit (Segregated Witness) was invented to decrees file size in Bitcoin transaction, this helps more transactions to get approved faster so the transactions will become faster, cheaper and better in overall performance.
Segwit will remove signature from transaction block and send it in different block, so basically if before transaction was sent in one block, now it will be sent in two blocks and the transaction block will have more space in it, this resolves the Bitcoin scaling issue.
As the transaction block size is limited to 1MB and the Signature block takes about 65% of that, removing it from the block makes sense.
Lighter transaction block. Lighter network connection. Faster Cheaper Better performance.
Litecoin has implemented already this, next it’s Bitcoin turn.