The convex hull of a point set is the outer boundary of the smallest convex set that encloses the point set entirely.
Consider this analogy: Imagine a set of nails nailed to a wooden board. If we stretch a rubber band around the set of nails, and let it contract, the rubber band will form a convex shape that entirely encloses the entire set of nails. The outer boundary, where the rubber band fits tightly around the nails, is the convex hull of the set of nails.
In 2D, the convex hull is a set of lines which forms the smallest enclosing convex polygon around the point set. In 3D, it is a set of faces forming the smallest enclosing convex polyhedron The notion of a convex hull can be extended into arbitrary dimensions as well, where the boundaries are referred to as facets, and the region is referred to as an enclosing convex simplex.
