A picture wired into this tex/Builder, as a texture.
Wire a picture into one of the tex/Builder's inputs and this node gives it as a texture, to read with the nodes that read any texture. code/TextureSample2D with a code/Sampler reads its colour at a uv, blending between pixels. code/TextureTexel reads one pixel exactly, at the pixel being written or next to it. code/TextureSize gives its size in pixels.
A 3D texture wired there (a tex/Volume, or a 3D tex/Builder) comes out as a 3D texture: read it with code/TextureTexel, or with code/TextureSample3D in VALUE mode at a uvw. Only a 3D tex/Builder can read one: in a 2D builder the build is refused with a message naming the input.
The colour comes out in linear light, whatever the picture holds: an 8-bit sRGB picture is decoded before anything blends it. A 32-bit float picture is refused, since a sampler cannot blend it.
Scenes you can open in the editor that teach this node.
This page is generated from the engine, so it describes the release you can download. The same text
is in the editor's Help panel next to the node itself.