What are combos and kill streaks?

I've noticed that, while I'm killing orcs, it will pop up with my current kill streak quite often, and, much more rarely, say my combo. I seem to get money for both and maybe points, but what are they defined as?

• A combo is when an orc dies from 2 or more methods at the same time. For example, a tar trap slowing them down and a clockwork mace gibbing them will count as a combo.
• A kill streak is when you kill many orcs within a small time period. If you continue killing orcs within a second (or so) of one another, your kill streak increments. Once you've gone a second (or so) without killing an orc, you are given a bonus based on the number of orcs you killed in that streak.