This question is a very, very big one. Steiner wrote many, many books and gave many, many lectures trying to explain a comprehensive and spiritual-scientific worldview. Obviously to explain it and the methods used to get to the conclusions would be a massive task, and to attempt that would be a whole series of articles in itself, we also understand that lots of Steiner’s work is rendered inaccessible due to wording, formatting, et cetera. So everything considered, (this is a very simplified thing, every single sentence and concept mentioned has hours and hours of content behind it and obviously cannot be explained in a paragraph or two. understand that this is just a glimpse at an ocean of a topic, and take everything here with a grain of salt. also if there’s a word you don’t understand make sure you google it) here’s the basics;

The world is the condensed expression of the work of hierarchies of spiritual beings. Forever in a state of continual evolution, the cosmos goes through distinct fractally embedded stages, separated by each other by periods of dissolution. The overall trajectory of the world goes from more spiritual to more grossly physical to more spiritual again. But the more spiritual state that is to be striven toward will have gained something incredibly important from Man’s sojourn into minerality, namely the completely free and individuated human “I.” The physical Incarnation of Christ (known in Anthroposophy as the “Mystery of Golgotha”) was the nadir in this overall trajectory, and out of it streamed the Christ Impulse, which directs humankind toward its future planetary embodiment, where the seeds for the new world will arise out of the thinking, feeling, and willing of Christ-filled human beings in completely free brotherhood. Something like that…