The idea is to eventually create an entire grid (constellation) of satellites in lower earth orbit with communication between satellites by laser, reducing the number of ground stations needed to manage the fleet. These satellites are not geostationary, like a lot of current telecommunications satellites. They are much smaller and in a polar orbit (meaning they travel north-south and complete a full circumnavigation of the globe in about 90 minutes versus geostationary satellites that travel west-east in 24 hours). Starlink satellites are also at a much lower orbit: only 400 – 700 kilometers, compared with 35,800 kilometers for geostationary satellites. This allows for much lower latency and the ability to provide a broadband connection to just about any location on Earth, once everything is in place.
The “stationary” part of geostationary describes how a satellite in this orbit remains fixed with respect to an observer on the ground – in fact, it is cruising around the world at the same speed that the Earth rotates, keeping the satellite at a constant longitude. This is an ideal orbit for communications satellites, since ground-based antennas can remain pointed at the same spot in the sky. In the case of Starlink, for full-time uninterrupted internet coverage, you need an array of satellites trailing one another: visualize it like a treadmill. You need to connect to one after another after another as they rise up over the horizon, climb high above, and then descend downward, falling out of sight.
You can read more detail about orbits here.
There are concerns with a large constellation of satellites in low-earth orbit: higher potential for collisions, given the sheer number of satellites, and ruining the night sky for astronomical observations. SpaceX has taken measures to address this including automated collision avoidance systems onboard its satellites as well as “VisorSats,” or, shields to reduce the reflectivity of the satellites. Looking at the positives, this creation of a global “blanket” of broadband connectivity will finally allow for reliable and fast connectivity – like never before. And as climate change continues to threaten communities around the world – often in remote places – these satellites can help communities get back online quickly in order to communicate important information during emergencies: https://www.geekwire.com/2020/spacex-provides-starlink-satellites-help-washington-state-towns-get-online-wildfires/