A floating license allows a flexible administration and usage as it ishosted by a server and distributed to compute clients on demand. Such a servermay manage the license requests for hundreds or thousands of software clients.
A node-locked license on the other hand is much more restricted as it can be used only on one pre-defined machine.
In any case, irrespective of the mode of the license, it is not limited to a certain number of users but to the number of concurrent processes. For example, if you have two licenses, at one time only two processes can be running - irrespective of the number of CPUs.