There are a few things you need to know if you want to edit text layers in Photoshop. First, the text layer is the layer that contains the text itself. Second, when you select a character or word from the text layer, Photoshop creates a copy of that character or word on the other layers in your document. Finally, when you paste a new line of text into a document, Photoshop pastes that new line of text into the text layer on top of the original one.
