It is not just virtual currency, but no you should not buy it without understanding it. I will explain what it is and why it is DOOMED unless they fix it.
Here is an analogy that is not perfect: A bitcoin is a piece if encrypted information. If you own the bitcoin, then you own the private key which can decrypt it. The bitcoin program protects the list of bitcoins. They are all kept in a very long ledger, a chain of blocks of information that has many copies, one in each computer that is part of the bitcoin process.
Three things make bitcoin possible. First, there are some math problems that can only be solved through making millions of guesses. Secondly, there are millions of computers owned by different people. Bitcoin consists of millions of computers striving to be the first to guess the solution to a math problem. It usually takes about 10 minutes for such a problem to be solved, but the length of time varies. Third, public and private encryption keys make bitcoins possible. A bitcoin is a piece of encrypted information. It has been encrypted with a public key. If you are the owner of the bitcoin, then you have the only private key that can decrypt it. Those are the 3 things that make bitcoin possible.
Every computer in a bitcoin network is busy 'Mining', running expensive electricity using programs. They are all working to guess the solution to a math problem that is inside the most recent bitcoin block of information -- and they are all checking on another's work to prevent any dishonesty. To be on the bitcoin network, your computer has to participate in this work of making guesses and guaranteeing honesty. Bitcoin is based on this, and if you are not running the program then you are paying someone else to do it for you. It is not free.
All of this only works if the computers keep mining day and night, nonstop; but there is a limit to the maximum number of bitcoins. Eventually when no one can make more bitcoins then people will stop running the bitcoin software. I think when people stop running the software, the currency will stop being secure. It will no longer be possible to prove the work and to prove that the bitcoin ledger is unchanged. It is DOOMED.