How do banks, hedge funds, and prop shops trade/invest?

How do different firms and desks within firms trade/invest? What is their performance? How do they measure their performance/risk/consistency? What is it like to work for them.

I'd like both comments about different industries from talking to people and actual experience (you should indicate this in your post).

I'll start:

Bridgewater (from talking with friends who interned, interviews, and on-site information session after receiving an offer):

Strategy:
They're a global macro hedge fund. They have a variety of funds, ranging from beta to alpha. Beta funds are ones marketed to institutional investors like pensions, and seek to capture a stable diversified return. Alpha is actively managed and contains their secret sauce. They invest based on trying to fundamentally understand international macroeconomics and use their proprietary data sets dating back to the great depression to backtest ideas.

Working there:
As an IA, you take a bunch of exams, and those who do poorly are quickly weeded out. The vast majority end up pigeon-holed into very specialized skill sets such as data analysis. The lucky few become idea generators and learn about the secret sauce presumably. There's a variety of subdivisions related to the operations, such as Trading (execution trading), research, sales (interfacing with investors), and one other thing I can't remember.

Comp:
95k base + 15k sign-on relocation bonus + an annual bonus of 0-40k (20k expected).

Stat Arb (some divisions of SIG, JSC, wolverine) (Information from talking to friends and interning and getting a full time offer):

Strategy: Market makers across asset classes. They're primarily market makers and arbitrageurs. Market making entails using the price of a product in a more liquid market to price a similar product in a less liquid market.

Working there: You start off with a side project. Your main focus is to kick ass in market making class. You have required reading and classes on option pricing. Even though you're not trading options, a lot of the ways of thinking about options carry over to market making for other securities. People can be kind of geeky. There's usually a bit of joking around when it's less busy.

Comp:
65-85k base + variable bonus. Comp structure is really variable. 500k as a third year bonus is not uncommon at some firms. SIG locks you in with a non compete for three years.

High Frequency (Getco, Jump) (From talking to employees):
?!?!?

They're black magic. Really heavy emphasis on machine learning. People apparently used to never leave Getco, but recently that's changed. Money seems to rain from the heavens?! I have no idea, who the fuck knows what black magic they work.