Light maps are when you use any lighting algorithm to generate a pre-rendered texture of all the lights and shadows in a scene. The result is a big packed texture and an extra set of texture coords on all the scene geometry that says which bit of the texture corresponds to what. You can use any lighting algorithm to generate the map, but presumably something that's too slow to use in real time, and that's in some way better than your real time shader.
Light maps only work on non-moving lights and non-moving objects, but they're usually combined with light probes, which are samples of what the shadows would be like in a given chunk of empty space if an object were there. Moving objects can shadow themselves using these.
Light maps can be combined with other lighting/shadow algorithms. For example you might leave out the direct lighting from the most important lights in your scene, and use shadow maps for those instead, so dynamic objects can cast shadows.
None that I know of. Your best bet is to find a post explaining what effects are in a renderer you like (such as the Godot one above), then look up the research papers those effects were published in.
I really like democoder Smash's old blog for getting an idea of the graphics coding mindset - https://directtovideo.wordpress.com/ . Another good source of what is possible and what it's named is the yearly Siggraph Technical Papers Trailer.
But it's usually going to come down to learning the names of the techniques used and then finding the papers.
Light maps only work on non-moving lights and non-moving objects, but they're usually combined with light probes, which are samples of what the shadows would be like in a given chunk of empty space if an object were there. Moving objects can shadow themselves using these.
Light maps can be combined with other lighting/shadow algorithms. For example you might leave out the direct lighting from the most important lights in your scene, and use shadow maps for those instead, so dynamic objects can cast shadows.