Muslim advice please help!!

Okay so my boyfriend is Arabic and Muslim (I’ve never been very religious) and we’ve been together for awhile I absolutely love and adore him and his family. When we get back from our vacation he asked if I would want to go to the mass (I think that’s what it’s called) so that we can eventually have sex and stuff...can someone please explain to me what this means? What should I expect? I would ask him but I don’t want to sound like an idiot 😩