SHA vs. Scrypt
While Bitcoin and a several other coins are mined using SHA-256, Litecoin and many other coins, use Scrypt. This are the two major hashing functions, but several different kinds exists and are used by other cryptpcurrencies such as scrypt-N and x11. The different hashing functions were adopted to answer concerns with the SHA-256. Before, individuals were able to mine Bitcoin with their GPU’s, which require a large amount of energy. But as Bitcoin grew in popularity, ASIC SHA-256 machine were built which  made GPU mining obsolete.

To give you an idea of just how powerful these machines are, a mining rig running 4 GPU’s would get a hash rate of around 3.4 MH/s and consume 3600kW/h while an ASIC machine can mine 6 TH/s and consume 2200kW/h. This effectively killed GPU mining and left many individuals worried about the security of the network. With less individuals being able to profitably mine from their home computer, the network become less decentralized. Scrypt mining was implemented with the promise of being ASIC resistant due to the memory problem it introduced.

Scrypt hashes require lots of memory, which GPU’s are already designed to handle and ASIC machines were not. However, Scrypt mining require a lot of energy and eventually scrypt-ASIC machines were designed to address this problem. At this point Litecoin considered changing their proof-of-work function to avoid ASIC mining. Scrypt also taut that their proof-of-work is much more energy efficient than SHA-256. Bitcoin blocks are solved at a rate of 1 per 10 minutes while Litecoin blocks are solver at a rate of 1 per 2.5 minutes.