TL;DR: When you complete the front-end as well as the back-end challenges along with the data visualization challenge, you will be able to obtain the Full Stack development certificate
In case you don’t know, technology stack just refers to a collection of technologies used hand in hand in order to perform a particular task like developing a web application. For example, LAMP stands for Linux, Apache, MySQL and PHP. Linux is an operating system, Apache is a web server, MySQL is a database management system and PHP is a back-end programming language.
Check out https://stackshare.io/stacks to know about the technology stacks that popular companies like Dropbox or Spotify use.