what is NBT tag and how do i use it

I know nbt store value but is there any special name to make it work?like,can i name a logic nbt tag to some random name like:arregggpoklkd?
will that work?and also,is there a nbt list(not the command nbt list,but like a list of working nbt tag that acquire specific name and letter arrangement,big cap or smol cap etc.)
and how do (return value) works?
I am using mcreator for a few years and i am still a noob
NBT tags are like a whole new world to me and i have a lot of things to learn