When you cut your grass too short it can leave brown or bare looking spots in the grass and lawn.
If you continue to cut the grass too short then it can actually kill off the grass by reducing the grasses energy reserves, weakening and yes killing the grass.
So be sure to cut the grass at the correct height and if you're noticing scalped parts of the lawn or the entire lawn is scalped then you're cutting the grass too short and should raise your lawn mowers deck height.
The height you cut your grass can depend on the type of grass your lawn has.
If you have bentgrass it can be mowed under 1/2″ while tall fescues should be 3-4 inches in height when cut.