16 pixels by 16 pixels is a common resolution for assets matching a low-res pixel art aesthetic. Although the assets may not be specifically 16x16, they are designed to work in a graphical setting where objects are around that size.
Uses two-dimensional "sprites", 2D images created and used on a flat plane, as opposed to the three-dimensional models or environments found in 3D games.
In the style of games made the 8-bit generation of game consoles & computers, or sometimes authentically created to run on original hardware. Common 8-Bit consoles include the Nintendo Entertainment System, Sega Master System, and the Commodore 64
