Q:

Purpose of EDB sockets

The plugs that are made for EDB sockets can be plugged into normal sockets as well, but normal plugs can't be plugged into EDB sockets. I'm pretty sure that they have the same voltage, as my devices with an EDB plug run just fine on normal sockets.
EDB sockets, mostly found in office buildings.

What is the purpose of EDB sockets?

A:

According to this site, this is unique to Denmark, and EDB denotes a socket that has extra filtering for equipment that might be sensitive to power-line noise, such as computer equipment.
I'm guessing that the filters may have limited current-handling capability, so the unique socket is used to prevent normal heavy loads from being plugged in. It would also prevent such loads from contaminating the other EDB sockets with noise.
Here in the US, all branch circuits, filtered or not, must support a minimum of 15A, so we don't need a special socket — we just color-code them to indicate filtering or other special treatment.

