This five minute youtube video explains linear color very well.
https://youtu.be/LKnqECcg6Gw
As for the myriad of color spaces, it's best to put them into two categories: working and exchange.
Exchange formats would be Video, Log, ACES and all of your projector/TV/whatever specific device is going to utilize or display the footage. The reason these are "exchange" formats is because they have various gamma curves and other business apllied to facilitate a specific need of the devlice. Video has a gamma curve and clips the image at 1. Log is the best way to store HDR data in an integer format. ACES is a giant space that can hold all the color values possible (up to and including gamma rays, so check your color before sitting too close to the screen), and so on.
You can work with varying degress of suceess in ALL of these, and as Joel notes in his video a bunch of nodes would prefer to work in one of these spaces. Nonetheless, it's best to consider them all to be incorrect to comp in, even if most of us have gotten away with it loads of times.
Working formats would be scene-linear with various primaries: ACES CG, Scene Linear Alexa Wide Gamut, etc. These formats will retain all the color values of the original image (brightness above 1, for example) and all math operations and blends will work correctly.
note that outside of film, most shops work in Video despite its shortcomings, and you could write a novel on the various pluses and minuses to each format.
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