Wikipedia is your friend. Google also.
"Blu-ray Disc (BD) is a next-generation optical disc format meant for storage of high-definition video and high density data. The Blu-ray standard was jointly developed by a group of leading consumer electronics and PC companies called the Blu-ray Disc Association (BDA), led by Sony and Philips. As compared to the HD DVD format, its main competitor, Blu-ray has more information capacity per layer, 25 instead of 15 gigabytes, but may initially be more expensive to support.
Blu-ray gets its name from the shorter wavelength (405 nm) of a "blue" (technically blue-violet) laser that allows it to store substantially more data than a DVD, which has the same physical dimensions but uses a longer wavelength (650 nm) red laser."
- Source Wikipeida