* Squirrels are very adept at climbing trees and often build nests (dreys) in the branches. They use trees for shelter, nesting, and finding food like nuts and seeds.
* Chipmunks are also good climbers, but they tend to be more ground-dwelling. They may build nests in tree cavities or under rocks, but they spend a lot of time foraging on the forest floor.
So, while they both may utilize trees, squirrels are more likely to live primarily in them, whereas chipmunks have a more mixed lifestyle.