What is a laptop? What is a tablet? For most people, the answers are obvious. But for Microsoft’s Surface line, it’s been a bit murky. Microsoft’s first attempt, the Surface RT, flopped. So much so that the company had to take a $900 million hit when it failed to sell them all. Microsoft’s second stab at tablets resulted in the Surface 2 with a sleeker design and better performance. It still wasn’t easy to use on the lap, and the lack of a full Windows OS meant it was never really a laptop and never really a tablet due to a lack of touch-friendly apps. While mistakes have been made along the way, there’s always been something charming and unique about the Surface and the fact that it’s not just an iPad clone. It’s never quite nailed what Microsoft was looking for, but there’s always been promise there, hiding underneath that kickstand. So now we have a third attempt, the Surface 3. It’s Microsoft learning from all of its mistakes and bringing lessons from the bigger Surface Pro 3 down to a smaller and cheaper $499 tablet. Because it finally uses a full version of Windows, you can now run…