What is... a CPU?
A CPU or Central Processing Unit is the brain of any computer, without the CPU the computer won't even boot up as it doesn't know how to think. So where the RAM is short term memory - CPU is the brain.
Just like our brains send signals or commands to our bodies like moving a hand or 'bending the knee' (game of thrones reference), the CPU is consistently sending commands to other areas of the computer based on what you're asking it to do.
So what is the difference between all the CPUs out there that various machines come pre-equipped with? Main differences include architecture, how many cores they have or even how fast they can think without really stressing out.
Architecture is determined by the different vendors that build CPUs and their ever evolving changes to squeeze the next bit of performance out of the next generation of their latest offering. These changes are often somewhat small but tend to snowball into noticeable differences in performance.
How many cores a CPU has is basically how many sections it has that you can send a task to and have it manage that (with one or multiple cores) to get the best result based on all activity happening at any one point in time. Most modern variants range from dual core (2) all the way up to 12 or even 16 cores. The interesting part of this is that the physical size of the CPU doesn't always need to change for there to be more cores. Technology is getting more nano-sized as it evolves and more cores can be fit into the same physical space the CPU had before.
Speed is something that over time adds up becoming noticeable when using particular programs or applications. Usually this cannot be modified so you will need to look at an upgrade if your current situation is not sufficient.
Note: It is dependent on what kind of CPU you have. Some manufacturers allow tech-enthusiasts to modify or overclock their hardware to squeeze even more performance out of them and perform tasks such as bench marking in a "who can do this better" kind of situation but this involves a lot of time and effort and is generally only an enthusiasts game.