NVRAM

Similar to PRAM

Key Combination: Option + Command + P + R

Stands for "Non-volatile Random-Access Memory", NVRAM is Random-Access Memory that stores information that's accessed during boot even before the OS X bootloader kicks in. NVRAM stores information for Volume, screen resolution, time zone information, and which disk to boot from. Corrupt NVRAM can cause glitches and prevent the machine from booting, and while clearing it may not solve the problem, its always a good first step.