A Human Design map, or BodyGraph, is a carefully laid out user manual that shows each individual how they are genetically designed to interact with the world, using their inner system. It describes the conscious and unconscious parts of ourselves, which themes are fixed in our unique system and in which themes we are sensitive to conditioning.

There are nine 'Centers' in a BodyGraph: the Head, Ajna, Throat, G, Heart, Solar Plexus, Root, Sacral and Spleen.
Two Centers, the Head and the Root, give pressure. The Head gives pressure in the form of mental inspiration, or questions we have about life that we want to find an answer to. The Root gives pressure in the form of adrenaline, to be able to act from the need to improve our living situation.
Four Centers are so-called 'engines' that generate the energy to act: the Heart, Solar Plexus, Sacral and Root. The Heart generates willpower, the Solar Plexus emotional energy, the Sacral life energy and the Root intuitive energy.
Three Centers are centers of consciousness: the Solar Plexus, Spleen and Ajna. In the Solar Plexus we are potentially aware of the 'Spirit', in the Spleen of our body and our intuitions and in the Ajna of our mind. We express these energies through the Throat Center in the form of conscious intelligence.
Finally, the G is the identity center, connecting us to love and our unique direction through time in space.
A more detailed explanation about the Centers you can find here.

The nine centers are connected by "Channels" that run from one "Gate" to abother Gate. In the BodyGraph there are 64 Gates and 36 Channels. The Channels form specific Circuits through which energy flows. They differ thematically, yet are interconnected.
Typical concepts, also called 'Keynotes', are associated with each Channel and each Gate. For example, the Keynote "Judgment" belongs to the Channel that runs from port 58 to port 18, with Keynotes "Vitality" (58) and "Correction" (18).
On the basis of these Keynotes you can already understand a bit what the theme is about, namely making judgments about the vitality (usability/health) of patterns or systems and understanding the extent to which these need to be corrected in order to achieve vitality.
This Channel is part of the Logical Collective Circuit that deals with logical patterns that are part of life. A pattern, something that repeats itself over and over in the same way, is only useful for survival and the improvement of living standards if it is perfected through correction.
Through these types of Keynotes, every Channel and every Gate is connected to a certain aspect of human existence.

“What you can rely on you’ve never relied on in your life. What you can’t trust you’ve been trying to trust all your life. What you’ve been trusting has never been you. What you’ve been ingnoring has always been you. Try to trust what’s really you and see what happens.”

~ Ra Uru Hu