What is meant by off-chain and on-chain transactions? I don't get the meaning of off-chain and on-chain in general.
Off-chain transcaction are those, that do not belong on Ethererum network, and are not visible there.
On-chain transaction are the ones executing on Ethereum network. Thats why you can track them using tools such as etherscan.io.
Usually off-chain transcaction are somehow "connected" to on-chain transcations (for example: storing tx-hash of on-chain transcaction in database or vice versa). This is useful, because not everything belongs to blockchain network, but we still want to "connect" data on blockchain to our data, stored in relation database or something.
Offchain transactions are used for micro payment in which two parties create a channel and transact micro transaction just signing and not broadcasting to main net .. Once they decide that they need to claim the exchanged value then they can post the transaction to Mainnet for mining and the value will reflect into their balances..