Why does enabling WEP still allow me to connect to my D-Link router without encryption?

Why does enabling WEP still allow me to connect to my D-Link router without encryption?

I have D-Link wireless router that I use for my home network. Everyone in the range of my wireless network can reach the internet, as it is unencrypted. I tried to set password on it, but nothing happens - and when you want connect to my wireless, it doesn't ask for password.