Hello and welcome
Hard fork and segwit2x is something very complex to understand if you are new, simply take it as something like newer android version.
Just like you can't use the apps made for old android versions in the new ones similarly after the hard fork the old rules won't be acceptable by the new ones.
Its primarily to make transactions faster.
Segwit is something that is primarily meant for increasing the transaction speeds, blockchains accepts 1 Mb right now and now it will accept 2 Mb, and other optimizations will be made so that the efficiency can be increased and speed too.