There are multiple ways to take screenshots on a Mac, including using Preview, Screenshot app, or built-in shortcut key combinations.
The common shortcut key combinations are Shift-Command-3 to capture the whole screen and Shift-Command-4 to capture a portion of the screen.
Adding the Control key to the shortcuts will copy the captured image to the clipboard instead of saving it on the desktop.
Using the clipboard method allows for easy pasting into applications for editing/viewing images or using Universal Clipboard for pasting on other Apple devices.