There is yet another excellent post from @lukew from where I have extracted some insights:

An intuitive design is invisible. Good design is invisible. It is like air conditioning –you don’t notice it until something is wrong.

A design is intuitive when the knowledge gap is really small. In other words, it’s easy for people to bridge from current knowledge to target knowledge.

Redesigns can increase the gap between current and target knowledge. People know how to use things and we switch things up on them.

We always want tool time to be lower. Amazon One-click eliminates tool time entirely. Walgreens scanning app for prescription renewals is another exmaple.

The “gap” between current knowledge and target knowledge is where design happens.

If you’re into interface design and UX read it all here.