The logic behind setting variables using logical operators? [Solved]

So, I've been in doubt about setting variables using logical operators, and I couldn't find any source about it. I've been scripting around and ended up with this:

block.Transparency = (activate and 0.75) or (not activate and 1)

This works, but it was a lucky guess. I really don't get the logic behind the code I made. Shouldn't the value be true or something? The only logical operator that I understand the use is not. I would appreciate if someone could teach me or link me to a page so I could fully understand on how to use logical operators for setting/declaring variables/properties.