Actually, in all Angular app, there is always a <𝐛𝐚𝐬𝐞> tag in the 𝐢𝐧𝐝𝐞𝐱.𝐡𝐭𝐦𝐥 file, in the project root folder:
Thig tag tells the Angular router how to build the URLs for the browsing,
by saying in which folder is the source code to do right the redirections.
If the folder which contains all your application is "𝐚𝐩𝐩" (which is the default folder by Angular CLI), you can just put the value <𝐛𝐚𝐬𝐞 𝐡𝐫𝐞𝐟="/">.
In conclusion, the <𝐛𝐚𝐬𝐞> tag enables the Angular router to build URLS related to the project "𝐚𝐩𝐩" folder.