Each year many children suffer electric shock or burns from inserting objects into electrical outlets on the wall. For newly constructed homes and remodel jobs in our area, electricians are required to use tamper resistant (TR) receptacles, also known as child proof outlets.
TR receptacles are designed so that a single object like a paper clip or pin cannot be pushed into the outlet. It has a dual spring loaded shutter that only opens when an actual plug is inserted into it.
If you have young children in your house this is a great safety feature and can be a lot more convenient than the little child proof caps that need to be put in all the outlets.
This photo shows one of many decor style TR receptacles available, this one installed in a home in Avondale, PA.