Before laying an egg the Queen places her head in the cell to see if it has been prepared for an egg. She then pushes her abdomen into the cell. As the egg is laid, she releases several sperm (she has sperm stored from her mating flight) that fertilize the egg.You will see her repeat this process two more times. During an active brood-rearing period, she will lay up to 1,500 eggs a day.

All the while, her attendants are grooming her. Notice the two bees in the upper-right corner. Their tongues are extended, touching and they are transferring honey from one to the other.
In the next video you will see more of this grooming in more detail while she lays an egg.