the texture node allows you to import a texture into your shaders.
When this node is used inside a material or particles systems, a spare param will be added to the node, allowing you to select the texture node. You'll then be able to read the texture values based on a uv input.
And note that the uv input does not necessarily need to be an actual uv attribute on your geometry. It can be any attribute, any globals (like time) or function.