Litecoin has three major differences with Bitcoin.

The Litecoin network aims to handle a block every 2.5 minutes, instead of Bitcoin's 10 minutes, that developers claim to allow for faster transaction confirmation. Advantages may include the ability to resist double attacks over the same period with Bitcoin.
Litecoin uses the cryptographic algorithm in its proven algorithm, a complex sequential memory function that requires asymptotically more memory than an algorithm not a hard disk memory.
The Litecoin network will produce 84 million Litecoins, or four times the currency, Bitcoin Network.