This "modern taxonomy" term was coined by Mariusz Banach and it's a great way of summarizing initial access strategy. He represents it as DELIVERY(CONTAINER(TRIGGER + PAYLOAD + DECOY)).
Delivery is the technique used to deliver the package to the user.Container is the container format used to package your files.Trigger is the means to trigger payload execution.Payload is the malicious code to execute.Decoy is a decoy file to present to the user.