They are simple 8 pin connectors, usually female, with 12 pins in 2 rows of 6, on 0.1 inch centers. Simple and easy to use.
There are also a multitude of little PMOD boards.
You can get a Digilent Pmod BB breadboard for $12 at the time of this writing:
And from Amazon (with prime) no less.Tom's Computer Info / tom@mmto.org