In my experience, the answer is pretty much anything they can get paid for. For example, we hired a big 4 consulting firm to help us do some software testing. T

In my experience, the answer is pretty much anything they can get paid for. For example, we hired a big 4 consulting firm to help us do some software testing. They were not great, but did something (I'm not sure what exactly, but they did produce some reports). We hired the same big 4 firm to come up with an algorithm for reducing financial risk weighted assets, and guess what, some guys from the testing team turned up! I was surprised, as there was no obvious crossover (and the lack of knowledge showed)! Anyway, the partner convinced us they'd do a good job so we played along for a bit. During this exercise, the guys did everything from manually typing in data to making a few spreadsheets to providing some opinion on financial rules and methodology. In the end, it was obvious they'd do almost anything (short of cleaning the toilets) to increase their billable hours. So you right to be confused, as the definition is flaky at best! Also, most consultants add very little value (especially big 4 firms), but every so often you do meet a superstar that's worth every penny.