If you aren't looking for a DIY smart mirror, you might be referring to:

How to Make a DIY Smart Mirror : 12 Steps (with Pictures) - Instructables

You can download the latest version from the MagicMirror² GitHub repository. Installation usually involves simple command-line prompts like: bash -c "$(curl -sL https://githubusercontent.com)" Use code with caution.

You can download hundreds of third-party modules to display weather, news feeds, calendars, and even Spotify playback.

To build your own, you will typically need to download and install the software via a terminal on a Raspberry Pi.

Once installed, you edit a config.js file to add your preferred modules, such as local OpenWeatherMap data. Other "Mirror" Projects

The software is free to download and community-supported. How to Get Started