What it is
Groundbait is crushed biscuit, fishmeal, sweet mix or a canal blend, mixed with water and used as feed. It is how you hold bream, how you put a smell in a swim, and how you bind a method if you don't want straight micros.
It is not something you put on a hook and hope. Mix it for the job: sticky for a method, emptying for a cage, overwetted slop for a pole cloud on some silver lines. Too much in a small commercial peg is how you fill them up.