like others have posted in its broadest terms meditation means different things depending upon ones own religion, cultural background, therapy approach, location...

for me, meditation is a state of mind where a person is totally relaxed. similar to being in a trance state of mind with one difference, the person meditating is in a state of focused awareness.. they are aware of whats going on in their body, whats going on around them in their environment, aware of people around them, aware of sounds, smells...even though everything around them is going on as it/they normally do the person is still totally relaxed.

some people choose a word or phrase to help them achieve total relaxation for example some people chant(say) or think the word oooommmmm, oooommmmm, others achieve total relaxation through focusing on their breathing, .... some people set a goal for example I know someone who prepares their self for meditating by picking the goal of lowering their blood pressure/heart rate. then she sits down in a comfortable position, closes her eyes, takes some deep breathing breaths, then when she is totally relaxed she focuses on her heart beat and listening as the heart beats slow down out of high anxiety beating rate to a normal slow beat. she also sets the goal of how long she will remain in this total relaxed state of mind.

When I meditate I achieve total relaxation by listening to a recording I made of me rowing my canoe around the lake. I focus on picturing myself on that lake again, in the canoe rowing. when I make the recording I purposely started out rowing as fast as I could and then slowing down to where there are spaces of time when no movement on my part was happening and the sounds of nature came through. During my meditation I dont think, I just listen. sometimes a thought unrelated to the recording or something outside myself will gain my thoughts. I just rein it back in by reminding myself to focus on the recording and relaxing. I do this meditation for work stress reduction. I have another meditation I do at bedtime which focuses on my breathing and relaxing my body for sleep problems.