No spoilers ahead, just an outline:
Mum is a comedy of sorts, centered around a recently-widowed woman and her family and friends. Her son is a bit dim and kind of shiftless, in a harmless way, and his airhead girlfriend is a hoot; she's always putting her foot in her mouth without realizing it.
Her little brother is recently divorced (I think) and is dating (married to?) a harpish social climber. He's probably the one who invokes the most pity in me, because even though he's far from perfect, he's genuine.
Her husband's parents are also around, typically inappropriate senior citizens (say whatever they feel like).
The main secondary character, though, is her and her husband's best friend. He's obviously been in love with her since the day they met, and everyone can see it but her. He's set to move to Spain, but keeps putting it off in order to stay close to her, but he doesn't have the balls to tell her how he feels.
It's not a laugh-track sitcom, just more of a year-in-the-life observational kind of thing.
"There is no bad weather, only bad clothes." - Unknown