"Sperren" means "lock". "Aufsperren" means "unlock". The "auf" here means to negate or "open" or something?
Sorry, I am not sure if this is an appropriate question to ask. Because the answer could simply be that, "auf" means nothing and "aufsperren" just means "unlock". You could say that it is just what it is and there is no need to ask what "auf" here means.
But for me I want to ask because if I know what "auf" means, and it will be easier for me to remember both meanings of "sperren" and "aufsperren". Otherwise I might confuse the two. And maybe there are other verb pairs similar to "sperren" and "aufsperren".