From LQWiki

uname is a command which prints system information like the kernel name. This can be very useful if you're trying to install or make a program and it requires headers for your kernal or similar. Instead of having to keep searching for your specific ones, if you have apt-get or similar program you can pass the output from uname to install whatever files are required for your architecture and kernel.

man page

Syntax

All about the running kernel:

$ uname -a
Linux kolossus 2.6.18.8-0.3-default #1 SMP Tue Apr 17 08:42:35 UTC 2007 i686 i686 i386 GNU/Linux

Revision:

$ uname -r
2.6.18.8-0.3-default

Machine type:

$ uname -m
i686