As Easy says.
The way to test for it is to open your engine lid and pull back and forth as hard as you can on the lower pulley.
you should *just* be able to feel movement. More than a tiny bit is a sign of a higher mileage engine but not necessarily a problem.
If you can see movement, then it is too much endfloat!
All the above is assuming you have a T1 engine (the one with the upright cooling / 2 pulleys on the front)