This is a recording.
The brake is part of the transaxel not the mower
You will find it behind one of the rear wheels ( usually right )
It is a small disc about 3" diameter.
Crud gets behind it and causes it to bind on.
Take some photos then undo the 2 bolts at the end of the caliper, do not touch the one in the middle. that is the adjuster & adjusting them is a PIA.
Take good note of where & how the return spring goes.
Behind the brake pucks are little metal shims try not to loose them .
Knock the pins out & clean them up but do not tube with grease.
Use dry chain lube from a push bike shop