Flickering can be a form of temporal aliasing. It's a similar phenomenon to spatial aliasing such as jaggies, but it occurs in time instead of space.
For instance, a common cause of image flickering in graphics is when the camera or geometry is in motion, and geometric features fluctuate in pixel size as they move. For example, imagine a railing with thin vertical bars. Depending where a bar appears relative to the pixel grid, it might get rendered as 2 pixels wide, only 1 pixel wide, or it might not appear at all. And in motion, it may rapidly fluctuate between these states, creating a visually objectionable flicker.
Another common cause of image flickering is specular surfaces with a bumpy normal map and a high specular power. The specular highlights can flicker in motion, due to their alignment with pixels changing from frame to frame.
Antialiasing strategies that address only spatial aliasing will often produce an image that looks good in a static screenshot, but turns into a flickery mess as soon as things start moving. This is one reason why temporal antialiasing has become popular in games in recent years.