The word "interface" is relatively geeky. Here is the definition from Merriam-Webster's dictionary.
An interface is where independent and often unrelated systems meet and act on or communicate with each other.
It's a powerful concept. Like I mentioned before, pretty much everything we do is a way to communicate with each other. And an interface is a middle layer that defines the qualities of that communication.
For example, a government website is one of the interfaces between citizens and the government. A celebrity's public image is an interface between their persona and their audience.
But I want to talk about the most common interface we use—how we want to be perceived by others. Some interfaces are simple, and some are somewhat complicated. People often think that if an interface is more sophisticated, there is more value behind it. It's because an interface defines an external perceived complexity of a person rather than the internal one.
On the one hand, many smart people are sophisticated, but it isn't easy to interact with them unless you're on the same level. On the other hand, many people tend to overcomplicate their interface—they want others to think they are more attractive than they are. Either of these isn't proper. Being authentic and keeping your interface simple is what makes you stand out.
Be sophisticated internally but easy-to-grasp externally. Make interaction with you easy for others.