Take a square of fabric, say 12x12 or even a fat quarter. Put it on your board, and set your iron straight down on it, without moving up or down or sideways. Lift iron, move to different section of your square, set it down again, until you've "pressed" the entire square smooth. Your square should still be square, not distorted. That's pressing.
Now, same square, but rumple or wad it up to create some wrinkles: Put the square on your board, set your iron down on it, slide the iron forward to the corner of the square, then back. Then slide it forward to the adjacent corner. While sliding, you press down somewhat on your iron. Continue to slide the iron in all directions until the square is smooth. When the square is smooth, you'll probably find it is also somewhat distorted, depending on the fabric quality and weave. That's ironing.
All my growing up life my mother worked in a laundry, running a shirt press. She taught me to iron and boy could she iron! She was a master at it; no wrinkles left in her wake. Learning to "press" instead was a bit of a challenge for me because my instinct is to "iron"...with a vengeance!
