Silo license activation


I have an old Silo license which simply relies on a serial number to install. I did not buy the new Silo/Milo version, so what does license activation mean ? Does Silo get tied to a single computer ? Does a user have to go online if wishing to install Silo to a different machine ? I heard activation only has to be done once, so what exactly does it do ? Many thanks for any help.