What is indirect lighting and why do I have to bake it in EEVEE? I have been using blender for a while .So I was wondering what indirect lighting in EEVEE was .Also I noticed that I can see the light produced by a lamp in rendered view without  even baking it.What does baking indirect lighting do?.It is better to understand things and use it .I guess it has something to do with how eevee works.How is it different from cycles?
It doesn't have anything to do with how eevee works, indirect lightning is referred to be as a lighting which doesn't directly fall on the camera and is reflected from some other surface. Eevee only approximates it and you get much more realistic and better results if you bake it, you can even limit the area for which it is calculated by using a light probe and then selecting bake all probes under eevee render settings.
Here is blender's official documentation about the topic:
https://docs.blender.org/manual/en/latest/render/eevee/render_settings/indirect_lighting.html