This is the first in a series of what I call Photoshop Fundamentals. It's where I'm not trying to teach you a specific technique, but instead attempting to inform you about a fundamental feature that is essential to understanding Photoshop at a deep level. We'll have to cover 4-5 of these fundamentals before we can start to combine the ideas together to get into deeper concepts in Photoshop.Note: This lesson does not have a PDF companion guide available. We include PDFs with all new lessons and will add them to lessons in our archive as time permits.