How to make a player buildable game?

So if the tittle diddnt make sense, basically im trying to figure out how, many games now have a edit mode type thing(not sure what to call it) where the player in the game can click a button and he can go and place down objects kinda if your in studio placing blocks. like in bloxburg the game lets the player click a gui and shows a grid for the area a person can build on. the user can then place down objects like chairs or tables and blocks from his or her inventory. this isnt a request for free scripts, i just need some help figuring out how i can do something similar to what i explained. links to articles or if you know how this works pls explain. thank you in advanced

(bassicaly what im trying to figure out is, how a player can place blocks down like btools from a inventory)