I'm confused about buying tires and rims. If I want a tire 25x10-12, the tire width is 10". Does that mean I need to find a rim that is also 10" wide?

It seems like a lot of aluminum rims are 12" x 7" wide, but hardly any tires are 7" wide.

 

Not sure if this will help or not but here's a chart. Basically, I think the rim width can vary about an inch either side of the tire width.

ATV Tire and Wheel Application Chart : ATV Tires Free Shipping : ATV Wheels : Mud-Throwers.com