How can I understand enzyme-substrate function?

The best way to understand the enzyme-substrate mechanism is to imagine a baseball glove, and a baseball (photographed on the screen). The baseball glove is designed to fit the baseball. Therefore, the ball fits perfectly into the glove. I want you to imagine someone throwing you a cricket ball, a ball with a similar shape and size. The ball would still fit in the glove, even if it's not made for the glove, right? Now imagine someone throws you a rugby ball, it is not the right shape or size for the glove, therefore it may damage the glove and cause it to change shape.
Now let's put this into context. An enzyme (pictured) follows the same principles. The enzyme is the baseball glove, the substrate is the baseball, as the enzyme is made to break down a particular molecule, just like the glove is made for the baseball. The substrate enters the 'active site' , just like the ball enters the glove.
NB: Active site = the part of the enzyme where all the chemical reactions happen which break down the molecule/substrate. You can think of it as the part of the baseball glove where the baseballs sits.
If a substrate which has a similar shape and size (such as the cricket ball in the example), it may be able to enter the enzyme, however no reaction will occur as the enzyme (glove) is not made for that particular substrate (ball). This is called a competitive inhibitor, as it competes with the correct enzyme, for the active site. If a substrate which has not got a similar shape and size then tries to bind to the enzyme, it can change or distort the enzymes shape, so that no molecule can enter the active site, therefore no reaction can happen at all! Think of it as a rugby ball coming along and hitting the glove so it can no longer catch baseballs, the correct ball! This type of action is non-competitive inhibitor, as NO substrate can enter the enzyme.
Competitive inhibitor = a molecule which binds to an active site on an enzyme, which causes no reaction to occurNon-competitive inhibitor = a molecular which binds to another site of an enzyme (called the allosteric site) causing enzyme deformation.