This is a way to bottle feed a breastfed baby to mimic nursing.
Paced bottle feeding is when you hold your baby upright during a feed, switch them from one side to the other midway through a feed, allow the baby to draw the bottle nipple into his or her mouth (without forcing it in), pace the feed over the same time a normal nursing session would take, and allow the baby to eat to satiation (that is, don’t make him or her finish the whole bottle if he or she doesn’t want to).
The whole point of paced bottle feeding is to help protect the nursing relationship. For example, if mom is nursing and needs to return to work, feeding her baby in this way will help make the transition back and forth from breast to bottle as seamless as possible. It will hopefully prevent bottle feeding from becoming much “easier” for the baby, so he or she will still have a good latch when nursing and won’t get frustrated with the pace of nursing.