How do production companies earn revenue and what is syndication?

I know companies earn revenue through advertising, but how do production Companies make their money? Do they sell all of their rights to their video/film products? What is syndication? Are ads sold on a local level through the local networks or are they sold by NBC/ABC or other big companies and trinkle down the network? How is the network structured?

Breaking into the world of production is difficult. Most people work in the industry, often for free to begin with and get to know people. Every Broadcaster commissions programmes, production companies, and everyone else who wants to break in to the schedules, send in programme treatments, a 3 page summary of what the program or series is about. This is the tough bit, these people receive hundreds of scripts all the time and of course are influenced by who they know, what is popular and who has a track record.
Advertising is another way in, but again, companies usually commission someone they have heard of. You can turn this on its head though by selling an idea into a company and getting them to commission you to produce an commercial for them. If you try and do this, you will fail, if you try again, you will most likely fail again. If you make it a mission and don't give up, eventually you will succeed, if not through trial and error, then through luck. The same cannot be said for the commissioning editor route, that is more hit and miss than sending writings to publishing houses.
The holy grail is to come up with a successful format which can be syndicated around the world at MIPCOMl, i.e Millionaire, desert island whatever, the bill, neighbours etc.