The most notable
difference between Bitcoin Core and its recently launched competitor Bitcoin Classic is that the former plans to roll out Segregated Witness through a soft
fork, while the latter wants to deploy a block - size increase through a hard
fork, meaning all full nodes
on the network need to switch.
The
difference between original bitcoin and all of these
forks is typically that the
forks will use different consensus algorithms, have different total supply caps, and so
on.