Question about Gigaset CL660HX handset (CH version)

This model of cordless phone is compatible with most DECT routers, but it is essential to check whether the Sunrise router supports DECT technology. If the Sunrise router supports DECT, you should be able to connect the phone without any problems. If not, you may need to use a separate DECT base station to work with this phone.

Could you explain to me what a dect base is?

What is a base