It's a matter of terminology. There's actually no US (or former Canadian) coin called a "penny"; the official name is "cent". However when the coins were first made in the 18th and 19th centuries they were large, about the same size as British one-penny coins. Because many people were familiar with the old British pennies, they continued to call the new 1-cent coins "pennies" as a slang term, and it's stuck ever since.
It's the same way we talk about "dialing" a telephone even though rotary-dial telephones haven't been in common use since the 1970s.
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A penny minted in 2013 is worth a penny, or 1 cent.
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In 1896 a penny was worth a penny. If you have a penny dated 1896 then it is worth more than that.
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A penny is worth 1 100th of a dollar, also known as 1 cent.
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