Texture array
A stack of identically-formatted textures addressed by an index and bound as a single resource — an atlas without the seams.
A texture array layers N images of the same size and format and lets the shader pick a layer with an integer index alongside the usual UV coordinates. Unlike a texture atlas, where tiles are packed into one big image, the layers have their own edges — so mipmapping and wrapping work without neighbouring tiles bleeding in. Terrain engines use them for ground materials, particle systems for flipbooks.
The limitation is that every layer must share dimensions and format; an array cannot mix 256- and 512-pixel textures. The feature arrived with OpenGL 3.0 (2008) and exists in every modern API. Anyone needing to mix sizes freely turns instead to bindless textures.