Skeuomorphism: familiar objects on a screen
When people talk about skeuomorphism, they are basically talking about a digital interface that looks like the physical thing it replaced. An old notes app looked like yellow paper. A bookshelf had wood grain. Audio software had knobs that looked like knobs you could actually reach out and turn.
This was useful when touchscreens were still new. If something looked pressable, you understood that you could press it. The interface was using an object you already understood to teach you how the digital version worked.
Neumorphism: soft edges and shadows
Neumorphism is not trying to look like a specific object. It usually uses one background color with a light shadow and a dark shadow, making a button look like it is coming out of the surface or pressed into it. It almost looks like everything was molded from the same piece of soft material.
I understand why people like it. It can look extremely clean. But this is also where it can create a real usability problem. If the only thing separating a button from the background is a very soft shadow, it may not be obvious that the button is clickable at all.
Glassmorphism: the frosted-glass effect
Glassmorphism is probably the easiest one to recognize. You have a translucent surface sitting over something else, and you can still see a blurred version of what is behind it.
The important part is not simply adding blur everywhere. The glass should make it clear that one layer is sitting above another. If every single card on the page is frosted glass, then none of them really communicates hierarchy anymore. At that point, it is just decoration.
Why did we move away from realistic interfaces?
People sometimes talk about skeuomorphism like designers collectively decided it was ugly and removed it. I think the more interesting answer is that people learned how digital products work.
We no longer need fake torn paper to understand a calendar or a wood bookshelf to understand where our books are stored. We already know how to tap, swipe, drag, and save things. The extra realism stopped being as useful, and simpler interfaces were much easier to adapt across phones, desktops, watches, and car screens.
But we absolutely still use skeuomorphic ideas. A camera icon still looks like a camera. Folders still look like folders. Music software still uses knobs and sliders. We kept the parts that help people understand an action and got rid of a lot of the visual clutter around them.
Comparing the three styles
Does it make the interface easier to use?
You can use any of these styles well or badly. A little skeuomorphism can make an unfamiliar control easier to understand. Glass can show that one surface is sitting over another. Neumorphism can work for a large, obvious control where the contrast is still strong enough.
But calling something glassmorphism does not make it good UX. If the text is hard to read, the button does not look clickable, or the user has to stop and figure out what the design is trying to communicate, the visual effect is not helping.