The UV map is a mapping between a flat surface of an image, and the not-flat surface of your object. Most shaders do rely on images even when they don’t look like they do - some of the hardcore utility shaders have image maps. Basically to work well with shaders you need to create a UV map that works well with tiling textures - take a “uv tester” checkerboard (google and you will find several) and apply it to your object, then tell it to tile 4x or more. If it gets weird obvious seams all over, it’s not a good UV map for shaders.
If your model is complicated, get comfortable with the process first by taking a cylinder and mapping that, and seeing what happens when you change the tiling. Look at the flat UV map and you will start to be able to conceptualize how UV mapping works. Good luck!