One more easy one for the veterans...

[lordvelius]

Can someone explain exactly how trade routes work? How much commerce they generate, etc.?

[Solver]

How much commerce they generate is shown in the city screen, that's a function of the distance between cities.

You start with 1 trade route per city. It means that each city can have 1 trade route. Cities that are connected through roads, rivers or otherwise will automatically establish trade routes with the most profitable city. Later, technology and civics makes it more trade routes.

If you have Open Borders with a foreign civ, trade routes may be established with them, which is usually good, because their cities are farther than your cities (obviously), which increases the revenue.

[lordvelius]

Thanks again! I'm trying to learn all the little things that I've been ignoring, but still want to have a full understanding of.