Resource plots are where you can go to gather tradeable goods and level up your skills. For example, a tree plot will enable you to cut timber and gain experience points that count towards your woodcutting skill. You do this simply by clicking the tree, after which you must wait a short cooldown period before clicking again. You won't gain resources 100% of the time, but with a little bit of luck you'll fill up your inventory in no time.
We are regularly adding new plots, so check back often for more opportunities to get resources.
To check your inventory and skills, visit your profile.