tachi-e
A style of character sprite popular in visual novels. They are typically (but not always) a straight-on full body standing shot of a single character on an empty background.
Tachi-e originated as character art in visual novels and adventure games. Often they are front-facing game CG sprites used during conversations with various prepared expressions and poses that can be switched as the conversation flows.
Many gacha games' skin illustrations will also have a tachi-e aesthetic, thus they sometimes also come with a faux figurine counterpart, usually being its evolved form. A clean character art removed from a faux figurine will also likely become a tachi-e if the character is standing (if they're sitting, it's invisible chair instead).
As a rule of thumb, if the image can be placed onto a random background with a video game dialogue box and the result will look like a fake screenshot, it's probably a tachi-e. The character is not required to be standing, nor be a full body shot (e.g. from the knee or waist up), as long as the art is reusable.
This tag does not apply to anything that's not a standalone character on an empty background. This includes multiple views, multiple expressions, variations, turnarounds, reference sheets, character profiles, character stats, faux figurines, dakimakuras, outlined characters, screenshots, fake screenshots, or images with non-empty backgrounds (zoom layers, gradient backgrounds, etc).
Examples
