On-chain
An on-chain payment refers to the use of the bitcoin blockchain base layer where all transactions are ultimately settled. On-chain payment fees vary based on the congestion of the network. Payments will take approximately 10 minutes to complete.
LN
A Lightning Network (LN) payment refers to the use of the second layer protocol stack on top of the bitcoin blockchain. Unlike on-chain payments, the fees are negligent, and the funds settle & clear instantly.