'We should catch up soon, mate.' Don't forget the comma before the word 'mate'. 'Mate' is a term of address meaning friend, pal, chum, 'amigo', buddy. It is widely used between men in the UK and Australia/NZ. And Ed is right about it only being used between males : one man would address another as 'mate', or a man could address his son or a little boy as 'mate' in an affectionate way. Women and girls never use the term.

It's commonly used between women in Britain these days too. Quite a few of my female friends call me mate and most of my male ones do.

Just to add... in Australian English, it is perfectly acceptable for a woman to use "mate" when talking to both male and female friends. We're all mates! :D

A 'mate' is your friend in this context, we also use it as a greeting in the UK saying 'alright mate' as a way to say hello. We also call people we have just met 'mate' as an informal way of referring to them, such as 'do you want a drink, mate'. People that you socialise with on occasions are also 'mates', you might play soccer with your 'mates' once a week etc.

"A mate" here means "a friend" or can even just "an other person" depending on context. I believe it is used just between men. We don't use it in this way in the US, and I've never heard a Canadian say it, so let's let a native from another British English based country jump in.