Bitcoins do not have value as a physical commodity like gold and are not widely accepted as legal tender like dollars.
Rather, Bitcoin appears to have value for the following reasons: It is popular.
In short, people accept and trade in Bitcoin because other people accept and trade in Bitcoin.
Bitcoin has a value due to its technology aspect. People are interested in decentralized, anonymous system like BTC and other cryptocurrencies have. And it's also an instrument of benefication.