Pectin is a mixture of poly- and oligosaccharides which make up the cell wall of many plants. For the human body, it is a fraction of soluble dietary fiber - fiber.
Pectins have the property of forming gels and jellies when they are present in an acidic environment, which is used when preparing jams.
Pectin is used when making homemade preserves and preserves. It replaces gelling sugars and gives the preserves consistency and a gel-like structure.