1) I mean events that either because we don't yet know or are unpredictable on nature, doesn't allow anyone to predict or replicate the result.
i.e. if you seed your computer randomness at the current microtime, it may sound like the result will be unpredictable, but if I know the second it was generated, all I have is to generate 1000 keys with the same algorithm within that second. A hard task by hand, but an easy pick for any computer.
Usually for entropy (other unpredictable events) computers uses parts of the user interaction. Now let's say we add to the previous example the current position of your mouse pointer. Well, it can be at any point in the Cartesian plane represented by your screen resolution. So let's say it's 1920x1080, so now I've 1920*1080*1000, or 2,073,600,000 keys to generate, at 2 Mh/s this would take 1037 seconds, or ~17 minutes to brute force, if I take more points from the cursor, I'll get a number so big that would take millenniums to break, this is actually how Bitcoin is kept secure, it's possibilities are a number so huge that we would be long dead before generate a significant amount of the possible keys.
2) Mine isn't "more random" than yours, the question is, for you to have mouse moves, to have the memory contents changing, to have all the entropy elements a computer being used normally has, someone has to be operating it, otherwise it's pretty much dormant, so it's pseudo-randoms will be weak due to lack of entropy elements.