SegWit transactions enhance the security of the Bitcoin network by enforcing signature checks before any other checks.  This prevents certain types of attacks and makes the network more resistant to vulnerabilities that exploit transaction malleability. Besides, SegWit's introduction was a soft fork, meaning that it did not require a majority consensus of miners to activate.  This made the upgrade process smoother and allowed for a more gradual transition.
And here is a link for beginner to learn Segwit, hope it will be helpful.
https://blockgeeks.com/guides/what-is-segwit/