Bitcoin is a digital currency that was created by Satoshi Nakamoto in 2009.It is created electronically and impossible to control it.This currency are not printed currency like dollars or euros.Running computer all around the world are producing it.Owing to this reason they are different from other currencies.
yeah,Bitcoin is a digital currency which has real value as other currency.But you can't print it like other currency.You just can imagine it 
Bitcoin is exchangeable currency that's why it's called digital currency.You can exchange it with other currencies .And it is the 1st decentralized digital currency,as the system of this works without central bank.I think,for this reasons bitcoin is different from others. 