When people talk about usability, they often throw around a jumble of words like heuristics, principles, guidelines, criteria, rules. They sound similar, but each plays a slightly different role in shaping how we design and judge digital experiences.

At its core, usability is about one deceptively simple question: can people do what they came to do, and feel good while doing it? Jakob Nielsen, Interaction Design Foundation, and others have tried to map this terrain through a set of “quality components.”

Let’s break them down:

• Learnability: How quickly can someone new to your design find their way? If the interface feels intuitive—almost like it “teaches itself”—you’re winning.

• Efficiency: Once people know the system, can they move fast? Think of a power user flying through shortcuts, or a shopper checking out in seconds.

• Satisfaction: Beyond function, is the experience pleasant? People don’t just want results; they want results that feel smooth, human, even enjoyable.

• Errors: How often do things go wrong—and how forgiving is the system when they do? Error-tolerant design doesn’t punish users; it guides them back on track.

• Utility: Does the system actually do what people need? Bells and whistles don’t matter if the core value isn’t there.

• Memorability: When users return after time away, can they pick up where they left off without re-learning everything?

Here’s the trick: these aren’t rigid rules, but lenses. They help us notice different qualities of an experience. Sometimes efficiency matters most (say, in emergency apps). Sometimes satisfaction or memorability matter more (a creative tool, a learning platform).

So when you hear heuristics, principles, guidelines, criteria, or rules—think of them as different doorways into the same house. They guide us not just in evaluating what exists, but in imagining what could exist. And the more fluent we become in switching between them, the better we can serve the people who step into our designs.