Grogs were five foot tall furry cones. Grogs were a telepathic race with a sessile adult stage and a sub sentient adolescent stage. They were highly telepathic and possessed of ESP. They used the telepathy to hunt, getting the prey to come to them, clean up around them and so forth. The other thing Gorgs do is think. Natural philosophers. Hurbirins considered them wonderful for observing lessor races. As this got the Grogs around, they didn't object. The Gorgs also had no objection to using telepathy to control other creatures. Grogs have not been seen since the Ane 9th Star Drive period. Their native star novaed some 5,000 years ago.
Grogs are an invention of Larry Niven appearing in his Known Space series of stories. They are pretty much lifted wholesale and used as an example without appearance. Yet another victim of the Kzin Question.