Each time a file is opened in VS Code, it appears as one of many toward the top of the window right above the text editor area. It shows the name of the file and the 'dirty' status. Over time as more and more files are opened and edited, the tabs accumulate and can only be viewed by horizontally scrolling left and right.
There are other ways to navigate to files besides selecting tabs of already opened files. So, if you'd like to reclaim some screen real estate and reduce the visual clutter of the tabs, you can turn them off.
Hit Cmd+Shift+P, then search for and go to Preferences: Open Settings (UI).
Search for Show Tabs which will show up under Workbench > Editor.
The default is Multiple. You can switch it to None to completely hide tabs. You can also set it to Single which will display file name and path for the current file, but eliminate the clutter of all other tabs.