On-chain: This term refers to activities or transactions that occur directly on the blockchain. For example, on-chain transactions involve the transfer of cryptocurrency directly on the blockchain without relying on external systems. 

Off-chain: In contrast to on-chain, off-chain refers to activities or transactions that occur outside the blockchain. Off-chain solutions are often used to reduce the load on the blockchain and improve scalability. Examples include state channels and sidechains.  

Open Source: While not exclusive to cryptocurrencies, open source is a key concept in the crypto space. It refers to software whose source code is freely available to the public, allowing anyone to view, modify, and distribute the code. Many cryptocurrencies and blockchain projects are open source, promoting transparency and collaboration.  

OTC: In the context of cryptocurrencies, "Over The Counter" (OTC) refers to the direct trading of digital assets between parties, often outside of traditional cryptocurrency exchanges. OTC trading is conducted directly between buyers and sellers, either through brokers or directly between counterparties. 

Ordinals: An Ordinal is information that lives forever on the Bitcoin blockchain.The aim of Ordinal theory is to give each satoshi individual identities, allowing them to be tracked, transferred, and imbued with individual meanings through inscriptions.