Marc Andreessen writes:
Bitcoin is the first practical solution to a longstanding problem in computer science called the Byzantine Generals Problem…The practical consequence of solving this problem is that Bitcoin gives us, for the first time, a way for one Internet user to transfer a unique piece of digital property to another Internet user, such that the transfer is guaranteed to be safe and secure, everyone knows that the transfer has taken place, and nobody can challenge the legitimacy of the transfer. The consequences of this breakthrough are hard to overstate.
What kinds of digital property might be transferred in this way? Think about digital signatures, digital contracts, digital keys (to physical locks, or to online lockers), digital ownership of physical assets such as cars and houses, digital stocks and bonds … and digital money.
All these are exchanged through a distributed network of trust that does not require or rely upon a central intermediary like a bank or broker. And all in a way where only the owner of an asset can send it, only the intended recipient can receive it, the asset can only exist in one place at a time, and everyone can validate transactions and ownership of all assets anytime they want.
Read more here.