3.96port a GROVE-to-HT3.96 interface convertor. The HT3.96 piece is 4 pins. HT3.96 is classed as Pluggable System Terminal Block catelog.
Terminal blocks are used to secure and/or terminate wires and, in their simplest form, composed of several individual terminals arranged in a long strip. Terminals are useful for connecting wiring to a ground or, in the case of electrical power, for connecting electrical switches and outlets to the mains