What is the break-in period?

Running-in period: Disc brakes require a certain running-in period before they can deliver full braking power. Do around 10-15 test braking operations with new brakes or brake pads.

Running-in time:
 Disc brakes require a certain amount of running-in time before they can deliver full braking power. Do around 10-15 test braking maneuvers with new brakes or brake pads.

Relevant articles:
Adjusting the V-Break , Roadworthy Bicycle