Bitcoin is ground-breaking open technology standard that allows people or companies to exchange digital tokens between each other without the use of any centralized server or entity in a guaranteed fashion. There is a finite number of "bitcoins", which are near mathematically impossible to recreate or duplicate, which make them a bit similar to gold or other precious metal while making it possible to transmit over the internet in a secure way.
Bitcoin was started in 2008-2009 by an anonymous person or group by the name of Satoshi Nakamoto. The value of the "currency" known as bitcoin is precisely linked to what people are willing to pay for it, and history has shown this value to be ever increasing over time, for the past 10+ years. To learn more about Bitcoin, visit this wikipedia article on Bitcoin.
Over the years since Bitcoin was invented, there have been numerous tweaks to the protocol. Some of these tweaks changed the format of the bitcoin address which is used for sending bitcoins from one wallet to another.
"Legacy" is the original bitcoin address format corresponding to the original release of the software in 2009. Legacy bitcoin addresses start with a "1" (one).
Segwit, or "Nested" segwit start with a "3" (three). This was the initial format implemented when the segwit technology was gaining popularity.
"Native segwit" addresses begin with bc1 and use the "bech32" algorithm. This is the newest bitcoin address format and is recommended going forward with new wallets created. This wallet address format results in the smallest transaction fees.
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