An anchor may be a temporary, permanent or a sea anchor. Its weight and configuration will depend on its intended use. An anchor's holding power also depends on the type of mooring and the line (chain, rope, etc.).
The anchor is a heavy weight intended to immobilize a boat at a specific location. The goal can be security, comfort, practical considerations or a combination of these, e.g., while moored overnight, while fishing, etc.
Anchors are usually made of metal. Lighter models (aluminum) derive their holding power from their form. The boat's movement during anchoring embeds the anchor in or hooks it to an object on the bottom.
Choice of anchor will depend on the size and weight of the boat, as well as the nature of the bottom typically encountered (sand, rock, vegetation, mud, etc.). The ideal anchor holds on all ground, is easy to handle, resists heavy tension, releases easily without damaging the bottom ecosystem and is easy to store aboard. However, the perfect anchor does not exist.