This tutorial has multiple sections since there are multiple methods to select files on Windows.
With the Mouse
Left Click
The simplest way to select a file is to just click on the icon that represents the file in the File Explorer using the left mouse button. A selected file will appear highlighted with a rectangle in the File Explorer's main pane.
When you click on a different file, that file will become selected, and the previously selected file will stop being selected. That is, with this method we can only select one file or one folder at a time. We can't select multiple files just by clicking on them.
Ctrl+Click
If we hold the Ctrl key before clicking on a file or folder, and then click on it, the clicked item will be added to the selection. This means that if we had one file selected before, we will now have 2 different files selected.
You can Ctrl+Click other files to select them as well, so you could have 3 files, 4 files, etc., as many files as you want selected simultaneously.
Ctrl+Clicking on a file that is already selected will deselect it.
Shift+Click
If we hold the Shift key before clicking on a file or folder, and then click on it, all items from the previously selected item to the clicked item will be added to the selection.
For example, imagine we had a folder with pictures of fruits, and this list of files was in alphabetical order. If we click on the "Banana" file, and then Shift+Click on the "Mango" file, everything from "Banana" to "Mango" will be selected, e.g. if there is a "Grapes" file between these two, it will be selected.
If we click on the first file of the list, and then Shift+Click on the last file of the list, all files will be selected.
After using this method, we can use Ctrl+Click to exclude some files from the selection. For example, if we didn't want "Grapes" to be selected, we could Ctrl+Click it.
Drawing a Selection Box
We can also select multiple items by drawing a selection box. To do this, follow the following steps:
1: move your mouse cursor to an empty area in the File Explorer's main pane.
2: press the left mouse button (or primary mouse button) and hold.
3: move the mouse cursor around with the left mouse button still held. You'll see that a rectangle will appear. Any file that this rectangles touches will become selected.
4: release the left mouse button when you have selected the file that you wanted to select.
Note that clicking on an empty area will deselect everything that is currently selected, so this method replaces the current selection with a new set of selected files.
Shift+Selection Box
If you click on an empty area while holding the Shift key, the files you had selected previously don't become deselected. We can use this method to add to the selection files that we cover with the selection box.
With the Keyboard
Arrow Keys
We can select files using the keyboard by using the arrow keys while the main pane of the File Explorer has keyboard focus. If we click anywhere on the main pane, it will have keyboard focus.
The way it works is a bit complicated to understand, since there are multiple things happening at once.
When we have a list like the list of files in File Explorer, one item of the list may have keyboard focus. The item with keyboard focus gains a border indicating that it has focus.
When we press the arrow keys in a list like this, the keyboard focus changes from one item to another. The item that had focus loses focus, and a different item gains focus. Only one element in a whole window can have the keyboard focus. This is completely separate from how the selection works.
When an item gains keyboard focus in a list, the default behavior is to ALSO make that item the selected item. So pressing an arrow key gives it focus, and giving it focus makes it selected, and deselects what was selected previously.
Ctrl+Arrow Keys
If we hold the Ctrl key while pressing the arrow keys, we can move the keyboard focus WITHOUT selecting anything. If you do this, you should see a border moving around from file to file, leaving the selected file behind.
Spacebar
Pressing Spacebar adds or removes the item that has keyboard focus to the selection. It selects it if it's unselected, and unselects it if it's selected. You can use this by holding Ctrl to move the focus around without losing the selection and then pressing space to select the files you want.
Shift+Arrow Keys
If we hold the Shift key while pressing the arrow keys, it adds all items from the item that had keyboard focus before to the item that gained keyboard focus to the selection. This works exactly the same way as Shift+Clicking. In fact, clicking on items gives them keyboard focus, so maybe it's not the clicking that selects items, it's gaining keyboard focus that selects items.
Home, End, Page Down, Page Up
We can use the keys Home, End, Page Down, and Page Up to quickly jump several items in the list instead of going one by one or line by line.
In particular, pressing Home key and then Shift+End will select everything from the first item to the last item.
Ctrl+A
The keyboard shortcut Ctrl+A selects all items in the main pane.
Danger: in the File Explorer, a keyboard shortcut for DELETING files is Ctrl+D. In some applications, this chord would mean "deselect all." In the File Explorer, it means "delete." Be careful not to press it by accident!