"Progressive lenses are a type of multifocal lens, meaning they provide vision correction to more than one distance.
They are available for both eyeglasses and sunglasses, and provide seamless progression of many lens powers for all viewing distances."

"The key to how progressive lenses work is getting used to looking through different parts of the lens when trying to focus on things far away or up close.
The way a progressive lens is designed means that viewing things at a distance is done through the top of the lens, and the lower you go, the focus shifts to things closer.
For reading and viewing things from up close, look through the lower part of the lens."

There are a few focusing tricks that help adjust to new glasses with progressive lenses. You can read about them or