Pain, pressure. This is thickening of stratum corneum as protective mechanism for i'll fitting shoes or abnormal bone stricter. These can be thinned with blade but the underlying gait disturbance has to be addressed with padding, corrective footwear , or surgery by a podiatrist if necessary.
Lotion or surgery. . Corns and calluses occur because of pressure points. Surgery can fix this, but if you're not ready for that, trimming them down and regular use of lotion may soften them to the point they don't bother you. You can also try larger shoes that don't rub against the painful areas! offloading orthotics can also help: see your podiatrist for casting.
Friction. Corns and callouses, the build up of hard tissue is due to friction. Many times there is an underlying bone problem that is creating pressure from the inside.
No problem. The problem with the presence of corn or callouses is pain. But that is expected. The skin thickens to protect the underlying tissues from damaging pressure. It is a warning of things to come. If no remedy is reached then the callus becomes painful and that, hopefully, will bring much needed attention to solving the problem.