There are a number of components that determine how well each computer performs.
For instance a central processing unit (CPU) handles all the processes running on your computer and deals with the interaction between the software and the hardware. The more processors your computer has and the quality of those processors largely determine how fast your computer will work.
The CPU isn’t the only important factor. Whilst the CPU governs the running of the processes on your computer the Random Access Memory (RAM) determines how many processes can be running at once.
When you run out of memory there is usually some form of swap file on your computer which is used to store idle processes. Disk swapping is bad because the slowest component on your computer is your hard disk drive. Recalling items from a swap file is bad for performance.