Regarding "a high concentration of satellites around the equator":
Geostationary orbit (~36,000 km above the equator) is the only orbit where a satellite appears to be stationary in the sky, so you can communicate with it using a small, fixed dish. In all other orbits you need a dish that can rotate to track the satellite.
This makes geostationary orbit highly desirable for applications with a large number of users who don't want to pay much for the service, i.e. satellite TV.
Other applications also benefit from being stationary: communications, weather and other long-term observation, etc.
And just outside geostationary orbit is another large concentration: this is a graveyard for old geostationary satellites. When a satellite is decommissioned, it is moved to a slightly higher orbit to free up its slot in geostationary orbit.
Geostationary satellites are concentrated on the equator (because that's the only place where an orbit can be geostationary) but that does not mean those satellites focus (i.e. aim their antennas and sensors) on the equatorial regions. GEO is so high, those satellites can be seen/see even high latitudes, just about everywhere except the polar regions. I'm at ~50º N, and my country benefits from geostationary communications and meteorology satellites, for example.