What is the difference between stamp and seal and chop ?Feel free to just provide example sentences.

Stamp can mean two things:
1) an official mark on a piece of paper that proves that the paper has been approved. E.g. if a company wants to sign a contract, they can either sign it with a pen, or they can use the stamp of the company.
2) A little piece of paper with a glue on the back that you glue to the envelope when you post a letter. Since you can buy the stamp only from the post office for money, this proves that you paid for your letter to be delivered.

In either case, the goal of the stamp is similar to a signature - it proves that the person who produced the stamp (company or post office) acknowledges the piece of paper or envelope on which the stamp is.

Seal on the other hand is used for proving that nobody opened an envelope. In the middle ages, they used soft candle vax and signet rings to close envelopes. They closed the envelope, put soft vax on it, pushed the signet ring into it. Then when the seal became cold, it became rigid. If someone opened the letter before the addressee did, the seal broke, so when the addressee got it, he knew that someone already opened it.

A chop is a small piece of something, I don't really know what it has to do with stamps or seals :)