learn syntax of query_String matching ( args)

I am new to nginx , i read a lot of tutorials and managed to set things up properly and fairly happy with my setup.
now i am trying to dig deeper into nginx so i enrich my knowledge and obviously accomplish my tasks

With that in mind, i need to learn how to match certain query strings, there's a lot of "snippets" online pointing how to match args,args_* and so on
though i cant find any tutorial that teaches the actual syntax or how to use proper conditions

if anyone can advice cof a place to start, i would appreciate it