To understand what is a lightning network we must check out its meaning first. According to Wikipedia lightning network is a ""second layer" payment protocol that operates on top of a blockchain. It enables instant transactions between participating nodes and has been touted as a solution to the bitcoin scalability problem."
So what are the advantages that the lightning network will give us:
1. A better privacy - This means not all transactions will be stored on the blockchain unless if payments were paid by both parties.
2. Faster confirmation of transactions - Transactions will be confirmed in just a click of a second
3. Smaller transaction fees - unlike the high fees today the lightning network may give us fair fees