A rough introduction to collision theory. Simplistically, collision theory treats molecules as hard spheres and says they will react if they hit each other with sufficient energy and in the correct orientation. The energy is required to overcome activation barrier. There is an analogy to pool and that you can think about trying to pot a ball. Needs two balls to hit, needs to have the correct energy and need them to be orientate correctly so that the ball goes in the pocket (but I'm avoiding saying direction as that is incorrect and causes confusion). TO accelerate a reaction you can increase the concentration as this increases the frequency of reactions. You can heat them up, the more they move the higher the frequency of collisions. The hotter the molecules, the more energy and the more chance of having sufficient energy. Or you could add a catalyst and this lowers the amount of energy the molecules require by changing rhetorical reaction pathway.
The last MakingMolecules #Chemistry #ChemEd #ChemSky of the year, but what a post, an org chemist introducing rates of reaction with collision theory! The pool analogy is shaky/orientation is important than direction/frequency not numbers). It's a vital topic but find a physical chemist for details.