Capture modes

Pick the mode from the menu-bar icon or with its shortcut. Shortcuts can be changed in Settings.

Area (⇧⌘4)

Press the shortcut. The screen dims.
Drag over what you want.
Hold Space while dragging to move the selection without resizing it.
Let go to capture.

A plain click does nothing, so a stray click never captures your whole screen. Press F to capture the whole display instead. Press Esc to cancel. Turn the crosshair on or off in Settings › General › Capture › Show crosshair.

Window (⇧⌘5)

The macOS window picker opens. Choose a window. The capture is that window only. Cancel the picker to stop.

By default the capture includes the window's shadow. To leave it out, turn off Settings › General › Capture › Window shadow.

Full Screen (⇧⌘3)

Captures the main display. With several displays, use Area and select the one you want.

Scrolling (⇧⌘7)

Select an area, then scroll. Frayo stitches the frames into one tall image. See Scrolling capture.

Record (⇧⌘9)

Select an area and recording starts. See Recording and GIF.

More Captures

Open More Captures in the menu.

Copy Text (⇧⌘2): drag over text. The text goes to your clipboard. Nothing is saved. See Text and QR.
Previous Area (⇧⌘6): repeats your last Area capture without selecting again. If that display is gone, you select again.
Scan QR Code (⌥⇧9): drag over a QR code or barcode. Wi-Fi, contact and other codes get a button. See Text and QR.
Open Image from Clipboard and Code Screenshot from Clipboard (below a separator) work from what you copied.
Self-Timer: pick an area, wait 3, 5 or 10 seconds, then capture. Useful for menus that close when you press a key. The delay is in Settings › General › Capture; Play sounds there turns the tick (and the capture shutter) on or off. It has no default shortcut. Assign one in Settings › Shortcuts.

Other ways in

More Captures › Open Image from Clipboard opens the image on your clipboard in the editor.
Capture Options › Hide Desktop Icons covers the icons with your wallpaper before a capture. Run it again to show them.

If a shortcut does nothing

Another app may own it. Frayo shows a notice at launch naming the clash. Change the shortcut in Settings › Shortcuts.