To add up, you also need to know the difference between libraries and frameworks. The easiest way to understand that is that libraries have a very narrow objective, and they tend to solve a problem or a set of strongly connected ones. On the other hand, a framework is the implementation of the whole language, which makes it a very powerful tool for developing a whole application, not only a small set of problems.
Now, that we have a better understanding about frameworks, lets get to it.
Express.js is a Node.js framework. If you are not familiar with Node.js at all, you can read about that here.
Most developers love express because it simplifies the way the request bodies are received and sent. More precisely, it does that without bothering you at all. In very simple terms, it receives all the requests for you, parses them in a way that is most appropriate for usage, and passes them to Node.js, letting you manipulate the given data, and send back a response, which is again, is taken care of entirely by Express.js. In addition, the one thing that I like personally is its unique way of implementing middleware functions. It is as simple as writing code in the same order that you want to execute the code. There are more points worthy of mentioning. However, the most important one is the tools. Tools allow you to work with the framework and add to its stack of features.
Vue.js is a framework designed for front-end developers. Like React.js, about which we will talk very soon, Vue is also implementing the virtual DOM, and as a result, letting your application update DOM components only when necessary. By adopting this logic, your application is way more, and I would even say, aggressively faster compared to the traditional HTML/CSS approach. It lets you render your application in a specific logic, and make no mistake; you are the only creator of that logic. It also has lots of libraries fulfilling its advantages.
Next.js is an excellent tool for skyrocketing your development process. It lets you use React.js on the front-end side. Next.js is a must for your production stage. It allows you to use server-side rendering along with the beauty of React. Next.js comes with a built-in tool for maintaining your application’s packages. It reads all your code and saves that in reusable packages for further usage. Due to that, you do not need to worry about the reusability of your code, though, no need to mention; this is not the same as following coding conventions and patterns.