How does "Compress Lightmaps" works?

I’m creating a mobile app, and I’m having problems with lightmaps compression. What does the engine when you disable “compress lightmaps” is something that needs to be set before building?? or is an option that works before packaging?? Is it possible to decompress lightmaps if they are compressed?? Also, is it possible to do a selective choice of lightmaps to be compressed??

Thank you very much.