Can anyone tell me the Meaning of "certificate" Treasury notes?

Question

I remember reading somewhere that silver Certificate One Dollar bills have a purpose or reason. Same thing with Two Dollar bills. What do the different color Certificates mean on different note denominations?

Sorry, my first question was not very clear, let us try it this way.
For example, what does the red seal on a Two Dollar bill represent? What does the silver seal on a One Dollar bill represent? Different Denominations have seals and different color seals, what do they represent?

Answer 1

OK, if we are talking about the seal colors, all the color means is what type of note it is. Follow the links for more info on each type of note.

Federal Reserve notes have GREEN seals. All current notes are Federal Reserve notes.

http://en.wikipedia.org/wiki/Federal_Reserve_Note

United States notes have RED seals. None have been printed since the Series 1966A $100

http://en.wikipedia.org/wiki/United_States_Note

Silver Certificates have BLUE seals. None have been printed since the Series 1957B $1.

http://en.wikipedia.org/wiki/Silver_certificate

Gold Certificates have GOLD seals. None have been printed since the US left the gold standard in 1933.

http://en.wikipedia.org/wiki/Gold_certificate

National Bank Notes have BROWN seals. None have been printed since 1934.

http://en.wikipedia.org/wiki/National_Bank_Note

Some silver certificates that were used to pay US troops in North Africa during World War 2 have YELLOW seals.

Answer 2

Two dollar bills are still in circulation because of two dollar bets at casinos. Silver Certificates are notes then ensure an owner to $1 woorth fo silver. This is so people could own precious metals but they could still be in government vaults. Also, if you have a 100 pound brick of silver you dont want to break it down into one ounce segments. However, the mint now makes silver bullion that people can buy and they dont make the silver certificates anymore.