So I hear this a lot during exercises, especially compound movements to keep my core engaged. Two different trainers I had worked with had taught me to do this by teaching me the pelvic tilt, where I lie down on the floor and kind of gently draw my belly button upwards by exhaling, using my lower abdominal muscles, which tucks the pelvis in slightly. They also may have suggested this since I have anterior pelvic tilt.
Then I read another post which said that engaging your core is like taking a dump, (sorry, TMI), so you inhale air into your stomach and kind of push it out.
The two methods seem opposing to me, and I am left clamoring for the right technique when I go through my strength training moves. Any pointers?