Many Earth-orbiting satellites are in geostationary orbits, which means they appear to hang directly over one particular spot on Earth.
They appear to be "stationary" with respect to a spot on the Earth because they have an orbital period of 24 hours, just as the Earth does. These orbits are also called "geosynchronous" because they have the same orbital period as the Earth.
Geostationary satellite orbits have very low inclinations, which means they orbit essentially directly over the Earth's equator.
Geosynchronous satellites are very useful for communications, since ground-based antennas can be aimed at a fixed spot in the sky. They are also employed for surveillance (spying!) since they can continuously "see" large areas of the Earth. This is, for example, useful for advance warning of missile attacks.
Some geosynchronous satellites, such as the GOES satellites, for example, are used for weather forecasting and meteorological research. Did you know that you can actually observe some geostationary satellites from the ground?
Note that, because they orbit over the equator, geosychronous satellites can only be used for communications by countries/agencies at lower Earth latitudes. (The geosynchronous satellites cannot "see" the polar regions of the Earth.)
Countries in higher latitudes use other types of satellites for communications.
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