Like many modern programs, Firefox runs multiple processes. Rather than running everything under a single process, using multiple processes allows each process to handle a portion of Firefox. For example, there may be a process to run the Firefox user interface, another process to load and display websites, and another process to run any add-ons you have installed. This approach offers a variety of performance, stability, and security benefits. For example, if a website causes the process displaying the website to crash, the whole browser won't crash. So, you make a long story short, it's normal to see multiple Firefox processes in task manager. This is also the case with other internet browsers. Hope this answers your question.