The triangle model is a way to show the three main things that businesses need in order to work well. It's like building with blocks - you need three blocks to make a triangle shape.
The first block is called "resources," and it means all the things a business needs to get started and keep going, like money, people to work, and things like computers and buildings.
The second block is called "activities," and it means all the things the business does to make its products or services, like designing, making, and selling.
The third block is called "outcomes," and it means all the things the business wants to achieve, like making money, helping people, or making the world a better place in some way.
When you put these three things together, you get a triangle that shows how a business works best when it has enough resources, does useful activities, and achieves good outcomes. It's like a recipe - you need the right ingredients, to do the right things, to get the best results.