What knowledge is needed here?

is just one way to receive and send messages

Reply content:

is just one way to receive and send messages

Ajax asynchronous request

html,css,js,jq,ajax

1. A certain language on the server side such as PHP java node.js
2.HTML
3.css
4.ajax

I will add a database, otherwise where do you get the information and store it?

This is an app interface, written on Android. PHP is used as the backend to provide json data processing requests, and a database is added to store the data. Just fine.