"At the weekend" is fine, despite the other comments to the contrary. (It is more usually rendered as "on the weekend" in American English, and given the timing of your enquiry, that's your main audience at the moment.) It could refer either to the past or the future, so you could equally well say say "I went shopping at the weekend" or "I'm going away at the weekend". "Next weekend" is a bit ambiguous, but I would say even as late as Friday, it would be taken as the coming weekend both in the UK and in the US.

Last weekend = previous weekend People would say "on the weekend" not "at the weekend". "On the weekend" differs from "this weekend" because "this weekend" refers specifically to the current weekend while "on the weekend" usually refers to the previous weekend so "last weekend" and "on the weekend" usually mean the same thing.

Lol, this is getting silly now, this is the third or fourth question in less than 24 hours about the usage of 'at the weekend.' And once more British people have to come in and say that 'at the weekend' is standard British usage to refer to the coming weekend.

Once again, be assured that AT THE WEEKEND is correct, even though users of American English will tell you otherwise. This weekend = the coming weekend Next weekend = a little ambiguous, but it usually means the weekend after this one. 'At the weekend' needs more context. It can mean 'every weekend', 'last weekend' or 'the coming weekend' , depending on the rest of the sentence. I usually play tennis at the weekend.= every weekend I played tennis at the weekend. = last weekend I'm going to play tennis at the weekend= the coming weekend I hope that helps.

I've never heard "at the weekend." If you want to say the "previous weekend" you would say "last weekend" or "the weekend that just passed" if you need to really specify what you're referring to. I would say your interpretations for "this weekend" and "next weekend" are correct.