VFX are digital effects made on a computer. VFX allows creators to create environments, objects, creatures, and even people that would be near-impossible to make in real life. 

SFX are practical effects or physical effects. These are made in the real world like props, make-up, animatronics, pyrotechnical, etc.

8 years old

Practice and more practice. You have to love this field otherwise you won't get too far. There is a lot of failure in this. Just like other things. I know it's not the answer you want but it is the right answer.