You will feel significantly different than before when your baby drops. You might be able to feel your baby's head low down in your pelvis, and perhaps you will have yet another increase in the frequent of urination because the baby will be putting much more stress on your bladder. Walking might also get more difficult. But other organs will get more space, including your lungs. Breathing might be easier after your baby drops, and heartburn might go away too. When in pregnancy a baby will drop into the pelvis depends on many factors. Perhaps the most important one is whether you are a first time mom, or have already been pregnant and given birth before.
Primiparas tend to notice their babies drop earlier on, while mothers with subsequent pregnancies might not experience their baby engage until they are already in labor. This is not a fool-proof rule, but rather a tendency. Every woman and every pregnancy is unique, and babies engage at different times in pregnancy. Lightening does not say anything about the length of your labor, or about when your baby will be born. Unlike, for example, losing your mucus plug or getting regular contractions, a baby that engages in your pelvis is not a sign of impending labor. But it is a signal that your body is moving in that direction, and that everything is going according to plan.