What is the meaning of Divisor?

In an expression involving division, the number by which another number is being divided.

An integer that divides another integer an integral number of times, the former being called a divisor of the latter.

A ring element which can be multiplied (by some other ring element) to yield a third ring element, the first being called a divisor of the third. If the ring is noncommutative, then one specifies whether a divisor is left, right, or two-sided.

Any of several kinds of formal object associated to an algebraic variety, scheme, etc., which play a role similar to that of homology or cohomology groups in the study of topological spaces.

An element of the free abelian group on the points of the space.
A Weil divisor: an element of the free abelian group on the codimension-1 subvarieties (or subschemes).
A Cartier divisor; see Cartier divisors on Wikipedia.Wikipedia