Photos can be reviewed by clicking the Playback button which is present on the back panel. Unwanted photos can be erased by clicking the delete button twice.

click to enlarge
While reviewing photos, you may find that certain photos will look better in sepia or monochrome or require editing such as red-eye correction, cropping, etc.
Movies can be played back while reviewing by clicking on the OK button to start and stop playback.
For in-camera editing, click on Menu and then navigate to the Retouch menu. Alternatively, while a photo is being displayed full frame, click on OK to display the retouch menu. Retouching saves a copy of the photo and leaves the original untouched.
Some of the commonly used retouching features are:
Red-Eye Correction: Can be used to remove red-eye from a photo.

click to enlarge
Trim: Used to create a cropped copy of a photo.
Monochrome: Converts photos to black and white, sepia and cyanotype.
Filter Effects: Can be used to intensify reds / blues / greens or else add the effect of a skylight / soft / starburst filter.
FishEye: Can be used to add a fish-eye effect.
Some of the other features in the retouch menu are Image Overlay, Small Picture, NEF (RAW) Processing, Straighten, Color Balance and Perspective Control.
These retouch options present within the camera can help perform the common editing tasks and can reduce the amount of post-processing required on the computer.