For the most part, all. The very base that was connected to roots would probably be too woody to eat. The leaves are very aromatic and work great in making broths, stews, and salads. The stems are easy enough to eat raw or cooked in a dish. Celery seeds should be ground before being used as a spice.
you eat the stem
stem
edible
the stem
yes
the celery "stick" is the stem and the leaves at the top the leaves of the plant; both the leaves and stems are edible
No celery is a plant with many edible stalks. However Celeriac (also know as celery root) a relative of celery but is not part of the same plant.
Edible parts . What about the curds? What are they when it comes to cauliflower parts?
There are several plants that have edible stems; asparagus and celery come to mind.
Celeriac is a term used for a certain type of celery that has swelled up and formed a large turnpike root. This is a edible, aromatic, root from celery.
Beans are contained inside the bean pod which is also edible. These pods grow on climbing vines.
fruit
no
Leaves.
Yes a celery stalk is absorbent becase of the Vessel tissue, Xylem, and the Phloem which are the parts of the stem of the celery stalk where the tubes that carry the water and minirals.
That dependes on the plant. With celery, you'd be eating the stalks, while with lettuce, you'd be eating leaves.