It's called the Filesystem Hierarchy Standard and the gory details can be found here
/usr/bin is for user programs.
/usr/sbin is for system programs - those that are used by admins, but not general users.
Both the above begin with
/usr and the standard states that these could be hosted on a shared server (using NFS, for example) and accessed by the various hosts on a network. The variants without the
/usr (that is
/sbin) are for essential programs that the system needs to boot (as the files in
/usr tree won't be available if they're on a NFS share).
/local/bin are for locally compiled user programs.
If you have an executable, which wasn't installed using the system's package manager, then I suppose you should place it in
/usr/local/bin if it's to be used by many users, or you could leave it in your home directory if it's only going to be used by yourself.