A common question, but the Teachers would give an uncommon answer.
First of all, ALL THAT IS includes things that are manifest, things that are not manifest, and the Absolute which transcends all concept and form and is only experienced (if you can even use that word, since it implies duality in our culture) as Self.
Secondly, of the manifest things, i.e. things having some sort of recognizable qualities, there are multiple universes and multiple realms in those universes where activities occur according to the laws which are in effect and define those realms. And within each realm there are different densities or valences, such as we have solid, liquid and gas. The Teachers say there are other “humans” in other realms and on other “earths”, though they may not look or function the same as we do or live under the same laws. Not to mention non-humans and non-earths.
Thirdly, all things have perceptibility and varying degrees of capacity to act upon or respond to what is perceived. Think of perceptibility as if you were a television set receiving multiple channels simultaneously. Not everyone (or every thing) receives the same channels and has the same sources of information to work with. With different inputs and different capacities, “reality” appears different to everyone and every thing.
Fortunately we earth humans share common mental and emotional resources so we can observe things in common, can converse and negotiate definitions of things, and decide upon what is significant. But it IS a process of negotiation since we live under the Law of Dominance, which via evolution approaches self-dominance vs. the dominance of others.
Now if all this detail interests you as it does me, you can read the transcripts directly, but, bottom line, it comes down to building an internal focus capacity: dedicating some time to read, wrestle with the concepts, take a step back, look at life, question everything and begin to explore the methodologies given by the Teachers.
But also bottom line, you don’t need to fully understand the details of the working of the cosmos to be watchful, appreciative, giving and joyful. Start there, stay there. The attitude will take you where you want to go.