Here's his presentation @ Google> https://www.youtube.com/watch?v=fp8H8EMm464
Marketing, Accounting, Sales, Business Development, Leadership, Public Relations, Customer Service, etc. All these are different, some seem overly similar and share common skills but there are subtle nuances that make them all unique. Small businesses a lot of times collapse Marketing & Sales and don't have a PR or BD team at all. Small to Mid-sized businesses will combine Marketing and Business Development many times as the skills overlap keeps it cost effective. Large enterprises have the luxury of knowing (and the ability to afford) that while the skills may overlap, you can't simultaneously be good at it all, so they break it up.
IMO, the best way to learn "business" is to recognize you can't do it all and be good from day 1. So pick 1-2 to work on, read and study. I personally suggest Sales and Marketing because without those you have nothing to Account for, employees to lead or customers to service. Read Crossing the Chasm (3rd edition), it is a great book on getting your product from the early adopters into the mainstream purchase cycle. It is also a quick read overall. As for Accounting, outsource it, when you are small it is cheap to outsource and you don't need the headache of jacking it up come tax time. But when you outsource it, spend time every week or month with the person doing the work and learn from them what they are doing and more importantly why. This lets you stay focused but still learn the basics of Accounting.
As for validating startup ideas. There are lots of methods, you should check out patio11's blog write ups as he talks about it when he started Appointment Reminder. In general though, and IMO, validating a startup idea is when people actually pay you for it, not just when someone says "cool idea". The difference seems minor but is huge, lots of prospects will tell you that it is an awesome idea, but when you say ok, fork over $50 or $5000 or whatever all the sudden they are like, yea, well I mean.... Same if you are seeking venture money, if you are not getting meetings or are being blown off you have to reevaluate your idea to make sure that you are pitching it correctly and that you are actually pitching something worth while. That doesn't mean you change ideas after the first 10 no's, just that you keep evaluating it to make sure you aren't too far off track and that you are communicating things correctly.
I think if you want to have a better basic understanding of how large economies work and how that effects political policy, I'd recommend studying macroeconomics.
If you want to understand the basic functioning of a business and how it relates to customers, I'd recommend marketing.
If you want to understand how businesses are evaluated, how they borrow and spend money, how they evaluate internal processes, I'd recommend finance.
If you want to understand how businesses optimize their processes, and design efficiency into their processes, then you should study operations research (aka operations analysis).
If you want to understand how a business keeps track of what it's doing internally, and how it's performing internally and how resources are allocated, and how it handles loans and taxes, then study accounting.
If you want to understand how to acquire talent and insure that employees are being treated in a way that respected laws on fairness, and how to manage worker's comp, pensions, health insurance, etc. then study human resources.
If you want to know how businesses handle their relationships with their communities and the media, then study public relations.
I hope this helps a bit.