Take a look at this picture I took yesterday and tell me if you can see any text wrote on it?
Unless you've got the eye of a hawk, then the answer will probably be no. However there *is* text on there. And I'll also tell you how to achieve this quick and simple way, which you could use if you create images yourself and don't want others taking credit for them - without having to plaster your image with visible text.
Ok, so you'll need an image, I will use my image above (just without the text)...
Use your text tool and write something (using BLACK as your text colour)...
Change the "Blending Mode" of your text from "Normal" to "Color" (near the bottom of the list)...
Now your text may have fully disappeared or may still be slightly visible. If it is still visible, move it to an area in the picture where you can no longer see it all. (Areas near light/grey colours work best)...
... and that's it! Your text is hidden, but still on the image! So what about reading your text? Well that's very simple too.
If you've still got that image open (so image and text layer are both seperate layers), then at the bottom of the "Layers" panel, click the "Create New Adjustment Layer" button and select "Hue/Saturation". Or if you've saved your work and already exported it as a JPEG and then reopened the image file, then just press CTRL+U (Mac: CMD+U)
Drag the "Hue" all the way to the right (+180) and drag the "Saturation" all the way to the right (+100)
... and there you go! You can see your hidden text in the image. :)