Total compensation is base salary plus stock/options. If your stock grant goes down by enough, total compensation may fall even if base salary went up.

I'm actually a stock trader, so it's even more skewed for me and would be a good example. Let's say I get paid $50 per year. At the end of the year, depending on my/our performance, I will get paid between $0 and $200 as a bonus, which I wouldn't count as part of my base comp.

Other forms of non-base include stocks/options/etc.

Performance bonuses?