Most magnets like the one used in refrigerator cannot lose its magnetism. Such magnet is called a permanent magnet
The fridge magnets are used in refrigerators to make the door able to be opened and closed with ease. 

Why magnets? Some naughty children play hide-and-seek and choose to hide inside the fridge. If from inside they can't open the fridge door, they will be suffocated in freeze to death.