Frames are a tool in the photographers composition toolbox. Frames help the viewer by creating structure that gives a sense of order and calm, other than guiding the viewers attention.
On top of the image itself being a frame, you can have frames that sub-divide the image frame into smaller areas that are easier to digest. The subjects that act as frames can be positioned in a way that give a sense of depth or 3D to the image – see the image above. Frames within frames can really compensate for the lack of a 3rd dimension in an image.
A frame does not necessarily have to be a square or a sharp edged object, it might as well be made up of several objects that together make up a frame – in the example below the leaves on the top, the concrete at the bottom and the steel pillars to the sides make up a frame that leads the attention to the boat and the sun in the middle.
A frame does not need to be square or symmetrical or complete: circles, triangles, L-shapes and even just a line can help the viewer read your picture.
When you start to become aware of frames within the images you see, you will notice frames and their effect more and more as you study other photographers work. This is a great way to enhance your skillset and build both implied and explicit frames into your toolbox as a photographer.
If you ask me, one of the masters of using framing in photography is Saul Leiter. In most of his images he uses framing as a very dominating tool to tell a story and guide the viewers attention. Have a look at these color images for inspiration: Saul Leiter.
Related reading
What is the rule of thirds in photography?
What are leading lines in photography?
