The first image shows licking the entire vulva from the bottom up, where the next shows focusing in on the clit by limiting the range of motion.
“When you’re ready to start oral sex, don’t go straight for the clit or the vaginal opening. Kiss her vulva all around to build anticipation and get your partner really turned on. Think of sex like a good movie: you’re waiting for the right moment, waiting for enough tension to build up, to kick into action. Start with one long, flat, consistent stroke from the bottom of her vulva all the way up until your tongue touches her clit. Then, with your tongue still in contact with her vulva, reverse the direction and go all the way back down. Drag the moment out for dramatic effect.” – Excerpt from Beyond Satisfied by Kenneth Play, Chapter 11: Oral sex, How to Give a Good Licking