You can use a five forces analysis diagram to show the forces impacting competitive rivalry, providing explanations of and notes about each.
Text in this example:
Five Forces Analysis
The strength of competition in the industry
Threat of New Entrants
The ease with which new competitors can enter the market if they see that you are making good profits (and then drive your prices down)
Threat of Substitute Products
The extent to which different products and services can be used in place of your own
Bargaining Power of Buyers
The power of your customers to drive down your prices
Bargaining Power of Suppliers
The power of suppliers to drive up the prices of your inputs
Adapted from Michael E. Porter, Competitive Strategy, Free Press, 1980.