Texture paste is used to create stronger or more defined shape than is possible with paint alone. There's an array of modeling pastes available from various paint manufacturers, in tubes and tubs. Some have 'bits' in them for added texture, such as beads, fabric fibers, and sand.
If you're using acrylics, you can mix the paint with the paste or paint over it. Check whether the paste dries clear or not before mixing paint into it. With oil paint you can paint over texture paste once it's dried as you would with an acrylic gesso. Modeling pastes can also be used as 'glue' in collage.