Lion Introduces Recovery Mode

Normally when you're having an issue with your Mac, such as a hard drive acting up, or bad permissions, you use the install disc for your current version of Mac OS to use repair and diagnostics utilities. However, Lion is a download through the Mac App Store, so how will users solve diagnostic issues?

That's where the new Recovery mode in Lion comes in. Just boot up your Mac while holding Command and R to enter recovery. Here you'll find all the same diagnostics and repair tools that were offered on your install disc. If you're working with a blank drive, one that doesn't have a recovery partition from the install of Lion, then you can expect your Mac to download the utilities from the internet.

With Lion, even troubleshooting has gotten easier. You can read Apple's official page on Lion Recovery here.
via tuaw