The triangle visualizes how much benefit a business, product, team, vendor, etc brings to its customer. Contrasted with what it cost the customer to achieve the value.
This visualization could represent a business investing in some security software or an individual person jumping from using a checkbook to an online budgeting tool.
In this case, the customer receives a tremendous time savings, as well as a reduction in risk. The customer gives up money to obtain these values.
Here is a similar looking graph, where the benefit and cost are reversed. In this case, the overall value received is substantially less than the value given up. This is the example that led me to create TRM, where we were focused on cost savings, but were not selecting the right cuts.