What does it mean when my cat has a bloated stomach and can hardly walk?

If this has come one suddenly (rather than slow weight gain from excessive eating), then I'd treat it as an emergency and run, don't walk, to the vet asap.  It may turn out to be just caused by worms, or it could indicate kidney failure or build up of fluid. Either way (and there could be other reasons for the bloating), he/she needs to be seen by a vet .... Preferably today!

Good luck