Years ago, you could go nearly anywhere outside of a city and have no cell coverage. Mobile networks have improved substantially since then, but there are still places that don't have adequate cell coverage for one reason or another. Thankfully, T-Mobile has an ingenious solution to fix this problem: satellite connectivity.
While some phones have had satellite connectivity for decades, modern smartphones only recently received the feature when Apple introduced it on the iPhone a few years ago. Since then, Google has adopted it on its Pixel phones, and T-Mobile has taken things further by expanding coverage to phones that were never advertised to have satellite connectivity in the first place.