If you are having a hard time remembering diffusion and osmosis I would recommend writing it down. Now if your issue is not remembering it but learning it, things are a bit different. So lets start with osmosis, H20 is the elemental name for water it has an O so H2O and osmosis go together. So in osmosis water flows from a high concentration to low. What that means is that if there is more water in one solution than the other on each side of the membrane water will flow towards the side with less water. So lets describe this more and less water I mean it is water it is all the same, right? Wrong, for example salt water has a lower concentration of water than distilled water. Well why is this you say, well that is because water is only the H2O, there are lots of other things in water such as salt and iron. If there is more of those other thing then there is less water. Now diffusion is different than osmosis because it deals with things that are not water. The concept though is the same, things will flow from high concentration to low. There are three types of diffusion: simple, facilitated, and active transport. Simple diffusion is when things simply pass in between the molecules in the cell membrane. It is simple so it requires nothing else for it to happen. Facilitated diffusion requires a protein to help thing pass through the membrane.  Facilitated starts with an f and fork starts with an f. You need a fork to eat food just as you need a protein for facilitated diffusion. Now active transport is a bit different. It moves things from a low concentration to a high. To do this it requires energy, which comes in the form of atp. Active transport basically shoves things into a cell. So when you are active you play soccer and in soccer you try and push the ball into the goal against what the defense wants.

Check out those examples:

Some active transport: