first of all we need to know what segwit stands for.
segwit stands for Segregated Witness. so now we know what segwit stands for lets take apart of Segregated Witness let start with Segregate.okay Segregated stands for separate and Witness is the transaction signatures so now we know that put them back together.in short it is the separation of transaction signatures.
How does it work than
It hides its increased block size by changing the definition of a block to be measured as one million units instead of bytes. The witness signature data would be separated from the Merkle tree record of who is sending or receiving the bitcoins. The witness data is moved to the end, and each byte of it would only count as one quarter of a unit. The overall effect would be changing the average block size to about 1.8 MB instead of 1. This means the existing Bitcoin protocol doesn't change, allowing it to work without as much upgrading of software. It also addresses signature malleability, by moving signatures out of the transaction data, making them impossible to change. The transaction ID is no longer malleable. This makes Bitcoin safer to use with Lightning Network, a way to speed up small payments by bundling them.
what does it mean
this mean that the fees for the transaction would be low and it would help with lightning network it also means that it is easier to add layer 2 solutions on top of the blockchain overall segwit is a good thing for bitcoin and as Microsoft said on chain scaling approach generally degrades the decentralized state of the network and cannot reach the millions of transactions per second the system would generate at world-scale.
the information that i have provided some parts are from Wikipedia and i have turned them in to my own word and add some more information on to it