To take a screenshot on a MacBook, there are several methods depending on what you want to capture:

1. Screenshot of the entire screen :
   Press and release Shift + Command (⌘) + 3.
   The screenshot will be saved to your desktop.

2. Screenshot of a selected portion of the screen :
   Press and release Shift + Command (⌘) + 4.
   The cursor changes to a crosshair. Click and drag to select the area you want to capture, then release the mouse or trackpad button. The screenshot will be saved to the desktop.

3. Screenshot of a specific window :
   Press Shift + Command (⌘) + 4 , then press the spacebar.
   The cursor changes to a camera icon. Click the window you want to screenshot. The screenshot will save to the desktop.

4. Using the Screenshot app for more options (macOS Mojave and later):
   Press Shift + Command (⌘) + 5 to open the Screenshot app.
   This app lets you choose to capture the entire screen, a window, or a selected portion. You can also record the screen and adjust settings like timer and save location.

Screenshots appear as thumbnails in the corner of your screen for quick editing or sharing if enabled.