What meditation is not:
Meditation is not a technique used to get us into some sort of emotional state. So if you are trying to get out of anger, or into a steady attitude of joy, meditation is not the way. It's not a form of escapism in which you can run away from your addictions, boss, annoyances, or problems. It's also not meant to put an end to your ruminations, although it probably can help with them, that's not the aim. It's not therapy in that if you sit down and meditate your problems will begin to resolve themselves from the effort. So don't assume meditation will bring that your way, either. And meditation is not a religion, although it can be practiced by individuals from a wide range of various religious beliefs.
There are plenty of ways to rest, relax, and find leisure, but these are not meditation, either. A guided imagery exercise is nice and even enjoyable and entertaining, but it is not meditation. So a "guided meditation" is a little misleading and leaves you vulnerable to the decisions, directions, and reality of someone else. It also keeps you from being aware of your true present moment, unless you just want to be aware of your relaxing and entertaining guided imagery, which is perfectly fine, but it's not meditation.
What meditation is:
Meditation is best thought of as ways in which you practice staying mindful, which means you are aware of the present moment as it is, not as it once was or how you want it to be. So it is a state of awareness and many meditation techniques are those that help you stay present and aware of your moment-to-moment existence in this life.
When you hear someone say they have meditation as a "practice" it means they are literally practicing mindfulness and possibly using mindfulness techniques to do that, and the reason this is important is because humans have a tendency to miss out on reality itself because they are either dwelling on the past and ruminating about the things that have already been, or they are worried and anxious about the future and those things that have not ever actually happened.
For instance, if you drive to the grocery store and upon arrival can't really recall all the traffic lights and things you saw along the way because you spent the drive angry about the thing your boss said yesterday, or you were busy ruminating about something a friend said about something you did or said, or your mind was focused on and worried about some upcoming event next week, then you actually missed out on that entire drive that was a part of your real and actual moment-to-moment life.
But with practice, we can all get much better over time at being present for our lives and actually aware of the goings on, the things sensed, the people coming in and out of our awareness, that series of traffic lights on the way to the store, and the true reality of every moment of our very short and limited precious lives.
So meditation is not the things that help us escape reality and the present moment, but it is awareness itself of the present moment. So if you are using the present moment to escape reality, you are not meditating, but if you are fully present then your meditation is sound.
You can find some great guidance as a beginner in this wonderful book by Thich Nhat Hanh, The Miracle of Mindfulness: An Introduction to the Practice of Meditation
Meditation is not really about seeking relaxation, but it does help with relaxation by bringing your mind to the present and pulling it away from future oriented worry which produces stress. You can find my prior blog entry about the ways meditation helps with relaxation here
"Just being in the moment in this place is the deepest practice of meditation" ~Thich Nhat Hanh
Thanks to luckey_sun for the great photo, https://creativecommons.org/licenses/by-sa/2.0/deed.en
