some mice have a wheel in the middle. generally what is this wheel for
Scroll wheel It is used, as the name suggests, for scrolling. It can often also be used as a third mouse button by pressing on it. The wheel is often – but not always – engineered with detents to turn in discrete steps, rather than continuously as an analog axis, to allow the operator to more easily intuit how far they are scrolling.
Paw The paw is characterised by thin, pigmented, keratinised, hairless epidermis covering subcutaneous collagenous and adipose tissue, which make up the pads. These pads act as a cushion for the load-bearing limbs of the animal. The paw consists of the large, heart-shaped metacarpal or palmar pad (forelimb) or metatarsal or plantar pad (rear limb), and generally four load-bearing digital pads, although there can be five or six toes in the case of domestic cats and bears (including giant panda). A carpal pad is also found on the forelimb which is used for additional traction when stopping or descending a slope in digitigrade species. Additional dewclaws can also be present.