In most cases, each computer will have more than one browser installed. This is common because any browser can be an alternative to browsing activities. The existence of several browsers can be another alternative if the browser used is problematic for some reason. Using more than one browser can also provide a different browsing experience.
Of the several browsers on your computer, one browser will certainly be your favorite browser for browsing activities and another may only be used occasionally. Due to being a favorite browser and one that is often used, you may already have a lot of bookmarks in that browser.