entering a file path into Finder or elsewhere?

You can type Command + Shift + g while in any Finder window or select "Go to Folder…" from the "Go" menu & type in or paste in a filepath. Press the "Go" button & you are there.

That particular keyboard shortcut is coded into the Finder, which is an application even though we don't usually think of it that way. In other apps, it might do something else, or nothing at all. For instance, in Safari, "⇧⌘G" is the shortcut for finding the previous instance in a search (it's on the "Find" menu item of the "Edit" menu).

You are right about the Keyboard Shortcuts section of the Keyboard system preference. Note that you can also create shortcuts as well as change ones that appear there, & they can be either "global," applying to all apps or specific to a selected app. However, the shortcuts you create will not override ones coded into an app.

If you click the purple question mark icon in the preference, the help topic that appears will give you a little more info about this.

CMD+Shift+g means to hold down the command & shift keys & then tap the "g" key. This shortcut is built into the Finder; you don't need to add it.

You can see this indicated in Finder's "Go" menu: next to "Go to Folder…" you will see "⇧⌘G" to help you remember this keyboard shortcut.

The hollow up arrow is the system wide menu symbol for the shift key. You will also sometimes see the ⌥ symbol (for the option key) & the ^ symbol (for the control key) in menus. They are all modifiers keys that you hold down while typing other keys to modify their behavior.