Meditation is one of the most basic tools in taking control of your own mind and life. Every major religion and philosophy has a version of it in their basic structure.
We will break it down into some basic categories for explanation here. This is not an exhaustive list and there are many more viewpoints than these out there.
This can range from just sitting for some quiet time to watch your own thoughts as they race past to a focus on your breath or a point on your body. The key here is calming and learning to focus.
Active quiet sitting
Although there are many words for this the basic concept is to begin with a seed question or word and just wait and see what response your sub conscious mind throws back at you. this is a good way to learn things about yourself you never knew.
This is a mental exercise that is the beginning of active control. Once you learn to make things real in your mind you can expand your imagination and creativity. It is also the first step in manifesting things in your physical world.
This is a broad description of meditations that can include contemplation on a single thought to drive it into the mind as a permanent habit of force in your life. Many of the older traditions use multiple focuses at this stage including repeated spoken words or mantras, hand positions called mudras and visualizations or pictures called mandala.