Lunar module disposition
The Lunar module lower sections (descent stage) were left behind on the lunar surface when the astronauts returned to lunar orbit. These were designed to act as "launchpads" for the ascent stages. The original plan for the ascent stages was to be abandon them in lunar orbit after return to the Command module and this was done for Apollos 10 and 11. However from Apollo 12 onwards it was decided to de orbit the ascent stages and impact them on the surface to create artificial "Moon quakes" which could be recorded on the seismometers that were left on the surface of the moon. The only two that this did not happen with were Apollo 13 and Apollo 16. Apollo 13's LM was bought back from the Moon as a "lifeboat" and burned up in the Earth's atmosphere over the Pacific Ocean after separation from the command module. With Apollo 16 control of the LM was lost at jettison so the impact manoeuvre was abandoned an the LM left in lunar orbit.
For the vehicles left in lunar orbit their reprieve was short lived. One of the discoveries of the Apollo programmes was that the Moon's gravity field is not uniform, there seem to be "mass concentrations" that cause the field to vary significantly at different locations. This becomes difficult for plotting a spacecraft's orbit (indeed this is how they were found in the first place). Because of these variations the ascent stages eventually crashed into the surface of the Moon.
Hope this of use to you.