Footwear refers to types of clothing worn on the humanoid body part, the foot. Typically, footwear comes in forms of shoes and boots. Historically, the practice of making footwear was a role performed by a cobbler or sandal maker. (DS9: "Improbable Cause"; VOY: "False Profits")
Footwear typically prevents unnecessary wear and tear on one's flesh from walking or standing. It can also be used to enhance performance of certain difficult tasks that one's feet cannot do by their genetic ability.
Examples of footwear
Starfleet uniforms include regulation black boots. Women's boots usually have a little higher heels than the men's. Starfleet uniforms starting in the 2350s included a loop at the bottom of the pant leg, which wrapped around the bottom of the boot to hold it in place.
One unique design was the footwear of the early-2270s, which was entirely different from any other Starfleet-issued boots. The footwear was the same color as the wearer's uniform, and the female variety had high wedge-type heels. (Star Trek: The Motion Picture)
While under the influence of the Saltah'na energy spheres, Jadzia Dax told Kira Nerys "You know what they say - put the shoe on the right foot first, but put the left foot first in the bathtub." Kira seemed confused after this statement. (DS9: "Dramatis Personae")
In 2371, after Tom Paris and Lidell Ren came inside from the cloud burst on Banea, he joked that "there must be a centimeter of water in my boot!" and he tried to take it off, but Lidell started kissing him. (VOY: "Ex Post Facto")