I don't track this stuff very well, but I get it. If you want a native app for Android and iOS, it sure would be nice to only have to write it once rather than two very different languages. Roughly double your reach without doubling the work. More and more of these things are reaching into desktop as well, meaning three targets for one.
This all starts to get confusing to me as apparently Ionic ultimately uses Cordova under the hood... just like PhoneGap does? Or something? But now Ionic is moving to their own thing? I guess it makes sense that there are some low-level interpreter things that translate web primitives to native primitives and that people build developer tooling on top of that.
Ever further outside my wheelhouse is Xamarin, which is Microsoft's take on unifying development on multiple platforms. The languages involved here are .NET and C#. It has all the same promises as everything else: build with this and it works everywhere! This is for developer convenience! It's fast and you will make amazing things with it!
I'm always of two minds with all this stuff. Some part of me is envious of really nice native apps. Most of my favorite apps on my phone feel very native, although I'm not sure I could spot which framework created them, if any. For example, I have a Dribbble app on my phone and I quite like it. It's simple and nice. I open it up and I'm logged in, which is usually not the case when I open a web app. It feels fast and has all the in-page animation stuff you expect from a native app. I totally wish we had an app like that for CodePen. Maybe if we were starting over today we'd write it in some cross-platform framework that targets all three platforms and maybe gives us some cool competitive advantage. Another part of me is like, meh, I'm a web guy on purpose. I think the native open web is the place to be and has the most longevity. A codebase that serves that well will be the least regrettable over time.