Synthesized answer
The provided passages do not contain the answer to the question "How would you explain the key concepts in your own words?". The passages only offer bibliographic information about a book, "An Introduction to a Theory of Abstract Objects" by Edward N. Zalta, and its categories and page count. There is no content from the book itself that explains its key concepts.
Synthesized from the book passages below. Chat with the book on Feynman for follow-up.
From the book
Title: An Introduction to a Theory of Abstract Objects by Edward N. Zalta Categories: Logic, Symbolic and mathematical Pages: 220