I've seen this home screen on internet and I wanted to know what are the small bars and triangles next to the app's icons ?
This comes from Action Launcher 3.
Those icons are features of the launcher called Shutters and Covers. As described here,
Both Shutters and Covers are indicated by small shapes in the corner of your icons.
See corresponding screenshot:
The equals sign means there's a widget associated with the app and you can swipe up on the icon to display its widget in a popup folder window. These are "Shutters"
Another main feature is "Covers" which is similar. It is basically just folders, but when you tap the icon it launches the first app instead of opening the folder. To open the folder you swipe up.
Action launcher received a major update sometime ago, and has been renamed just Action Launcher (the 3 dropped).
According to Android Authority,
Not only does it have a bunch of new features, it also includes a new logo for the app and a new name... The app is dropping the “3” part of its name and it will simply be called Action Launcher from now on.
Additionally you'll notice the shutters and covers have a new polished design with smoother edges, than previously before.