Contrary to the traditional MPAs, SPAs are designed specifically for web-based applications. The SPA fetches all the data when you first load the website in the browser. Once all the data is fetched, you don't need to fetch any more data. When any other interactions are done, that data is fetched over the internet, without having to send a request to the server and without reloading the page. This means that SPAs are much faster than the traditional MPAs. However, since SPAs fetch everything at once on the first load, the first page load time could be slow. Some applications that have SPA integration are Gmail, Facebook, GitHub, Trello, and so on. SPAs are all about making the user experience better by putting the content on one single page and not making the users wait for the information they want.
The following is a sample diagram of how SPAs work...