system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:How does the Deep Space Network (DSN) work?
gpt
It is like when you are trying to hear something quiet and far away and you turn your head to point your ear right at it to hear better.  The Earth is like an always turning head and the radio antennas of the DSN are like three ears on different sides of the Earth so we can hear from any direction.

Every spacecraft has a radio like E.T.'s Phone Home device to call back to Earth and tell us what they have found but they are so far away it makes them hard to hear and if too many try to talk at once we cannot understand any of them.  Each spacecraft has to be given a schedule of when to talk so that we can hear them each one at a time or three a time if listening with all three ears.  

The radio signals take time to travel such long distances at the speed of light, so although we hear the calls from two different spacecraft at different times, they may have actually been sent at exactly the same time, but each took a different amount of time to travel to us because of the different distance between Earth and each spacecraft.

For example, we have the Cassini spacecraft in orbit of Jupiter, and the Mars Reconnaissance Orbiter around Mars.  Right now both planets are in the same direction so at any time the same DSN antenna could hear both for 8 hours until the Earth rotates so the next antenna faces Mars and Jupiter, and so on for all three as the Earth rotates.

As of today:
Mars is about 223 million miles from Earth and radio signals take 20 minutes to travel to us

Jupiter is about 556 million miles away and radio takes 50 minutes to travel

Say both need to transmit to us for 30 minutes each day, and we want to listen to them right after lunch at 1:00pm.  We could schedule them both to transmit at exactly 12:40.  From Mars it would take 20 minutes and we would hear it at 1:00 and the spacecraft would talk for 30 minutes, at which time the signal from Jupiter would be right behind it and arrive at 1:30, because it took 50 minutes to travel to us, so we can hear each separately and clearly.

Of course we have more than two spacecraft to listen for, so this process of scheduling is constantly ongoing for each spacecraft and each antenna, as spacecraft orbit planets, planets orbit the sun, and everything rotates, so the schedule constantly changes.  Yet another of many reasons math is so cool that we can figure out how to do that right.