#666190 | Hokenshitsu no Dekkai Sensei | 1,132 The piece above her underwear is the [garter belt], and the [garter straps] connect the belt with the stockings #665435 | Kurau Girl | 6,469 here shows a type of [garter], which is connected to the stocking by a [garter strap] #663918 | Immoral Game Master | 淫亂悖德．遊戲管理者 | 3,832 the woman in the middle has another type of [garter] (fabric as opposed to leather) which is not* connected to anything else via straps #384305 | Utakata ~Uraaka DoM Haken OL Onaho Chou… | 60,552 the decorative top-part of stockings, though similar in looks, do not count as a [garter] since it isnt a standalone band (thin within reason) #421551 | Seikoui Jisshuu | Sexual Experimentatio… | 68,920 another type of [garter] without [straps]

After perusing Wikipedia and other sources, it seems there are three main categories garter strap = the thin, belt-like strap that falls vertically or diagonally downwards anywhere below the waist garter = a "sexy" band wrapped around the thigh. Can be a gyaru putting a scrunchy on her thigh, can be the common marriage accessory garter belt = the lingerie piece specifically worn on/around the waist almost all belts will contain straps, and many garters contain straps as well