I would explain it a bit different (a bit more technically but I hope still understandable, maybe ELI10 
):
A hard fork is a situation where new blocks are attached to the chain according to new rules that are incompatible with the old rules.
Legacy clients would build and validate blocks that are following the old rules. But beginning with the "fork block" these old rules would not be viewed as valid anymore by the "new" clients, so they would reject all blocks coming from legacy clients.
Segwit2x is a hard fork, but as there are many Bitcoin users that prefer to stay with the original chain, a likely outcome is a chain split, because many users (probably the majority of non-mining nodes) would never upgrade. So both chains continue to exist, but one of them will take the lead.
I predict the leader will be the "legacy/Core" chain if Segwit2x does not reach at least 85% (maybe only 90% would be enough) of the hashrate for more than a few days.
):A hard fork is a situation where new blocks are attached to the chain according to new rules that are incompatible with the old rules.
Legacy clients would build and validate blocks that are following the old rules. But beginning with the "fork block" these old rules would not be viewed as valid anymore by the "new" clients, so they would reject all blocks coming from legacy clients.
Segwit2x is a hard fork, but as there are many Bitcoin users that prefer to stay with the original chain, a likely outcome is a chain split, because many users (probably the majority of non-mining nodes) would never upgrade. So both chains continue to exist, but one of them will take the lead.
I predict the leader will be the "legacy/Core" chain if Segwit2x does not reach at least 85% (maybe only 90% would be enough) of the hashrate for more than a few days.