Meditation was a mental technique performed by living beings. By meditating, Force-sensitives could reach a deeper state of relaxation, making them easier to connect with the Force with a clear mind. This technique, which consisted of opening a connection to the Force, was something even the eldest of Jedi Masters studied over a lifetime.
On the other hand, whereas the Jedi meditated to quiet their minds and connect with the Force, Sith Lords meditated to concentrate their anger, their fear, and their hatred into a pure point of ruthless power within them. As meditation was to have a stronger and more direct connection with the Force, it could sometimes affect one's surroundings without the practitioner's conscious control, usually causing surrounding objects, or even the practitioner themselves to levitate.
The basics of Jedi meditation were to focus on whatever emotions were uppermost in one's mind, to be honest with oneself about the feelings one experienced and their effects. Then, one was to let each emotion go—the goal being to make oneself an empty vessel that the Force would be able to fill with peace and serenity.