What are the 2 types of BLS?

Could you elaborate on the two distinct types of blockchain ledger systems, specifically focusing on BLS? I've heard about the term but am unclear about its variations. Are you referring to the public and private variants? Or perhaps there's another classification that's relevant in the context of cryptocurrency and finance? Clarifying the distinction between these two types of BLS would be invaluable for those interested in blockchain technology and its applications.