Thanks.I think he means groove and the ability to play behind the beat, ahead of the beat or on top of the beat. It is weird because this all happens in a split second. If it isn't played right the drummer might drop or add a beat. When I think of "pocket" I would listen to "I Got the Feelin" by James Brown.
Despite my curmudgeonly protestations, I do think I vaguely understand what the guy is saying. What's happened is that the language has changed over the years. A bass player I work with asked me the other day what the heck people mean by talking about grooves and pockets. In his favor, his English is weak, and maybe there's other terminology in Spanish, but he is a decent bass player working for hire in multiple bands. I laughed and told him that as far as I can discern, groove is the beat and pocket refers to us playing together.
I also get behind, on, and ahead of the beat to some extent. Playing behind the beat doesn't make much sense to me--that is lagging and sounds bad--but there may be times it's in order, perhaps to create anticipation. Playing ahead of the beat makes more sense to me, and I suspect that I do that sometimes. This I think drives the band. But for the most part I think playing dead center on the beat is the job, and anyone who gets so far off that they're dropping or adding beats is a mess, in my opinion.
I love James Brown and consider some of his stuff some of the most challenging. It can be complicated rhythmically and therefore needs to be delivered precisely. If any member flubbed the rhythm in "I Got the Feelin," the song would no longer be James Brown's but Patsy Cline's "I Fall to Pieces." I mean, really, that song could fall apart in a heartbeat. That it hangs together is a real testimony to the entire rhythm section. However, just me, I'd call this tight rather than a pocket.