can you please tell me what will happen in a hardfork ?
in a hard fork an upgrade is added to a project. there is no consensus on what to call hard fork but usually not being backward compatible means it is a hard fork.
in a cryptocurrency, hard fork is when you change something that makes previously invalid rules, valid.
why is the hardfork need for a coin?
a coin is a program, a lot of lines of code. sometimes you need to "upgrade" that code to fix a problem, or add additional features, solve some issues,... so you make a hard fork.