Someone who is an expert gamer is someone who can pick up most games easily. An expert gamer typically has experience in many types of game play meaning it takes them less time to grok games. An expert can also be extremely good at one game or one type of game.
A novice gamer is someone who cannot pick up games easily. They don’t spend much time playing games or have very little experience meaning it takes them much more time to grok a game than an expert. They may never grok a game at all.