I found a reference here which has some diagrams or concept maps about the extremely difficult Whitehead's process philosophy and its relation with other philosophers and schools of thought. The author appreciates Whitehead's effort as:
There can be no doubt that Whitehead’s philosophy is a valiant effort to bring value or the human quest for meaning and fact or the scientific quest for truth together in a single scheme. The scheme as a whole cannot be understood and appreciated by looking at it from a single angle. Taking human consciousness as a starting point for obtaining a phenomenological description of a paradigm event of cosmic process, both at macro-scale and micro-scale, as well of human as of divine reality, was brilliant.
In summary below are a few key metaphysical concepts of his process philosophy according to wiki reference here:
For Whitehead's ontology of processes as defining the world, the actual entities exist as the only fundamental elements of reality. The actual entities are of two kinds, temporal and atemporal. With one exception, all actual entities for Whitehead are temporal and are occasions of experience (which are not to be confused with consciousness). An entity that people commonly think of as a simple concrete object, or that Aristotle would think of as a substance, is, in this ontology, considered to be a temporally serial composite of indefinitely many overlapping occasions of experience. A human being is thus composed of indefinitely many occasions of experience.
Inherent in each actual entity is its respective dimension of time. Potentially, each Whiteheadean occasion of experience is causally consequential on every other occasion of experience that precedes it in time, and has as its causal consequences every other occasion of experience that follows it in time; thus it has been said that Whitehead's occasions of experience are 'all window', in contrast to Leibniz's 'windowless' monads. In time defined relative to it, each occasion of experience is causally influenced by prior occasions of experiences, and causally influences future occasions of experience. An occasion of experience consists of a process of prehending other occasions of experience, reacting to them. This is the process in process philosophy.
The actual entities, the occasions of experience, are logically atomic in the sense that an occasion of experience cannot be cut and separated into two other occasions of experience
Whitehead's abstractions are conceptual entities that are abstracted from or derived from and founded upon his actual entities. Abstractions are themselves not actual entities. They are the only entities that can be real but are not actual entities. This statement is one form of Whitehead's 'ontological principle'.
Concrescence is a term coined by Whitehead to show the process of jointly forming an actual entity that was without form, but about to manifest itself into an entity Actual full (satisfaction) based on datums or for information on the universe.[19] The process of forming an actual entity is the case based on the existing datums. Concretion process can be regarded as subjectification process.
Finally Leemon McHenry's book The Event Universe: The Revisionary Metaphysics of Alfred North Whitehead as commented here may be helpful to understand Whitehead further.
Everything in the universe from medium-size dry goods to planets and galaxies, is interpreted as patterns of properties that are repeated in event sequences. 'Things', as we ordinarily understand them, are postulated by Whitehead to be relatively monotonous patterns in events. The advantage of Whitehead's approach is that it provides an ontology that can coherently explain and unify the macroscopic world that we inhabit with the microscopic world of the physicist.
