denotation - it is the main meaning of a sign. The dictionary definition of what you are seeing. This is basically the first level to a sign.
connotation - The secondary meaning to a sign. It is the other meaning behind the sign, sometimes based on a viewers experience. It can be how a word is said or in what context it is being said.
anchorage - text that fixes the meaning of an image. It sort of forces the viewer to think a certain way about an image. It is hard to veer from that meaning once an image has some sort of anchorage or anchor.
relay - Text that adds some extra meaning or connotation to an image. Without this text the viewer sees the image as it is. A relay can change the viewers perception of an image or story, it takes the image further.