"1" is where your needle comes up through the fabric.
"2" is where it goes down again.
Super easy! Make a small stitch (1-2) about the length of a (long) grain of rice. Good. Next, bring your needle up through the center of that stitch you just made (3). Come down again like you did with your first stitch, and repeat. Continue with every stitch that follows (coming up through the last one you made). That’s it! You will need to work with a divisible floss so you can split them with your needle as you work. Looks impressive (like a tiny chain stitch), but is super simple! (This is also the very first stitch I learned, and the one I use the most). Want to see what it looks like stitched?
The petals of the rose are worked in a split stitch. You don't have to learn any more stitches beyond this one if you don't want to. You could embroider for the rest of your life using only this one sweet stitch.