If you aren't looking for a DIY smart mirror, you might be referring to:
MagicMirror² is the world's most popular open-source software for building smart mirrors. It operates on a and uses a two-way mirror with a monitor behind it to overlay digital information onto your reflection. Key Features Project: Mirror Free Download
To build your own, you will typically need to download and install the software via a terminal on a Raspberry Pi. If you aren't looking for a DIY smart
Once installed, you edit a config.js file to add your preferred modules, such as local OpenWeatherMap data. Other "Mirror" Projects Project: Mirror Free Download