Differences b/w Unix and Linux

Hi, I know this might sound stupid but I am just wondering what are some of the key differences between Unix and Linux. I know Linux is basically a clone of Unix.. (they probably have the same file system too?) I am thinking of learning linux.. so i just wanna know if i learn linux, would i be able to work off unix easily? (btw, do they have the same command lines? similar at least?) well, your pointers would be greatly appreciated... thanks...

"so i just wanna know if i learn linux, would i be able to work off unix easily?"

if this is what you want to do... grab slackware 8.0

Yeah, almost everything in Linux interface is the same as Unix. There are a few subtle differences though.

What are some of these subtle differences, may I ask?

Let's see...I'm not a Linux/Unix expert. You can look it up on the internet...Go to google or something.