The project management triangle is a way of thinking about projects and making sure they are successful. It's like a triangle, with three sides, each side representing a different part of a project. The three sides of the triangle are cost, time, and quality.
Cost means the money that you need to pay for the people, materials and equipment needed to complete the project.
Time means how quickly you need to finish the project or how long it will take to complete.
Quality means that the project is done to a high standard, with good materials and attention to detail.
For a project to be successful, you need to think about all three parts of the triangle - and make sure you get the right balance between them. You can't just focus on one side of the triangle at the expense of the other two. For example, you can't spend too much money on making something really good quality and then not have enough time or money to finish it.