Landed on the near side. But they orbited around to the far side. When the spaceship was around the far side of the Moon, radio transmission got cut off and was a bit of a tense moment until the radio transmission resumed when they came around again.

They landed on the near side because

• It was much better known - they had maps of the entire near side to large scale. We didn't know what the far side looked like at all before the lunar missons
• Radio communication with Earth.

They landed at partial phase, not full phase. Because when the sun was directly overhead it would be too hot, a challenge for their cooling systems.  While if they had landed at night locally, then it would be very cold, and in darkness.

The lunar "day" lasts for 14 Earth days so they had plenty of time to explore before the daytime sun got excessively hot for them.

This is the phase of the Moon as seen from Earth on the day of the Apollo 11 landing, from

Phase of the Moon on July 20, 1969, at 20:18 when the Apollo 11 astronauts landed on the Moon. http://tycho.usno.navy.mil/vphas...

As you can see neither near nor far side was dark at the time. It was quite close to half phase.

Of course no part of the Moon is in permanent darkness. But we always see the same side of it, and at full Moon we see it at full phase.

Actually we see a bit to either side because of lunar libration. As seen from Earth the Moon looks like this:

The far side of the Moon is however "radio dark" - it's the most sheltered place from terrestrial radio interference. You'd be shielded from it 24/7, and during times of full Moon, shielded from interference from the sun also. Much of the radio spectrum is hidden from our view on Earth because of terrestrial radio interference.

You could build simple telescopes on the far side, just trail wires across the surface of the Moon, to observe in low frequencies.

The Moon also has Peaks of (almost) eternal light  at its poles, and just next to them, craters of eternal night. Amongst the coldest places in the inner solar system. Mercury also has similar craters of eternal night and may have ice there. And Deimos, the outermost of the two Martian moons also has permanently shadowed craters.

The Moon may have large quantities of ice - quite possibly in layers giving a detailed history of our solar system so of great scientific interest - and also - useful as a source of water. We have pretty good evidence suggesting large quantities of water ice at its poles.

So - though not a dark side, it does have permanently "dark patches" at its poles and almost permanently lit patches too..