Startup programs are programs and software applications that are set to automatically startup when your computer turns on. Most programs display a small icon next to your system clock, showing you what is running. These programs are usually set on the Startup list as a default and they run in the background anytime your computer is on, regardless of whether or not you are actually using the program. This is set as a convenience for the user, but what most people don't know is that these programs all take up much-needed system resources, substantially slowing down your computer.
When programs are removed from your computer's Startup list, they are still installed and work as normal, but they just won't start automatically. This lets you run only the programs that are necessary, giving your computer a performance boost.