What is a celery heart ?
The heart of the celery is the tender, milder inner stalks. Their color is usually cream-to-yellow. I prefer the heart, myself--I find the outer stalks to be somewhat bitter, though they work find as aromatics in cooking.
It's the heart of the celery.
The outer stalks tend to be crisper and a little tougher, so once you've taken off a layer or two of the outer stalks you are left with the sweeter more tender stalks....called the heart.
The heart is the innermost part that is left of the plant when you pluck all the stalks off. It is very pale in comparison & looks like new plant growth.