Search notes:

Windows: Settings -> Update & Security -> For developers / Use developer features

Settings -> Update & Security / For developers allows to select a how apps can be installed. This selection is intended for development use only.

There are three options from which can be chosen:

Microsoft Store apps	Apps can only be installed from the Microsoft Store
Sideload apps	Apps can also be installed from other sources that the user trusts.
Developer mode	Any signed and truted app can be installed and advanced development features can be used.

See also