Paint is a liquid, colored substance you can use to decorate or protect a surface. If you want your bedroom walls to be bright purple, you need to buy some purple paint.
Artists use paint to create landscapes, portraits, and other styles of paintings, and house painters use paint to coat and protect the wood siding on houses. When you paint, you make a painting, or cover something with paint: "First I'm going to paint your portrait, and after you paint that wall in your kitchen, we can hang it there." When someone "paints the town red," they don't literally paint anything — they just go on a celebratory spree.