'Pay to the bearer on demand' just means that you need to pay the bill to the person you are owned money to. The person will be noted on the bill.
On the paper currency of many countries, there is a phrase that says "will pay to the bearer on demand." This means that the money is essentially nothing more than a promissory note but it is backed by gold owned by the government.
1963
If it has a green seal, it's worth $12 to $15.
A "pay to the bearer on demand" $10 bill is worth its face value of $10. This means that anyone presenting the bill can redeem it for $10 in legal tender. The value remains unchanged unless it is damaged or if there are specific collector's interests that might increase its worth. In general circulation, however, it holds the same value as any other $10 bill.
I promise to pay the bearer on demand the sum of ...
Many, many different bills carry that legend. Please post a new question with the bill's date, denomination, seal color, and whether there is a small letter next to the date.
A "pay to the bearer on demand" statement on a $100 bill indicates that the bill can be exchanged for its equivalent value in cash upon request. Therefore, the bill is worth its face value of $100 USD. This statement was more common in older currency notes when they were backed by a physical commodity like gold or silver, but today, the value of the bill is based on the trust in the issuing government and its economy.
That phrase appears on many older bills. Please check your bill again and post a new, separate question with its date, what letter if any is next to the date, and the bill's seal color.
All silver certificates and many other older bills carry that phrase so more information is needed. Please post a new question with the bill's seal color, and whether there is a small letter next to the date.
A Bill of Exchange is a payment document for a trade in goods. It is a written negotiable instrument in the form of unconditional order signed by the maker directing a certain person to pay a certain sum of money on a certain date payable on demand or expiry of the fixed period only to the certain person or order of the certain person or the bearer of the instrument.
The only $20 bills printed in the 1934 series were Federal Reserve Notes so I'm assuming that's what you have. In worn condition most of these retail for about $22 despite their age. In better shape the retail price depends on what series letter, if any, is next to the date. Series D bill retail for up to $30 in excellent condition, Series C up to $28, and the rest up to $24. FWIW, the last $20 silver certificates were issued in 1891. The wording "will pay to bearer on demand" is found on older FRN's but was removed from later series.
1928 US five-dollar bills with red seals were common in circulation. For this reason, they only command about $7, unless they are in mint condition with no folds, then they would be able to get more.