They include Food, Wood, Stone, and Ore (Gold is not counted as a “resource”).
All four are produced in your fields.
You can find your current totals listed near the top of your screen.

Holding your mouse over its picture, shows you more information about it.
When the capacity limit is reached, your fields don’t produce any more.
The hourly production is the amount you produce per hour.
With food, the troop’s upkeep shows how much food your troops are eating each hour.
You can see hourly production more easily on the Supply tab at the bottom right corner of your screen.