In algebra, infinity is usually expressed as the range of variables, that is, variables can approach a certain value infinitely, but they will never reach this value. For example, when we say that a series is infinite, it means that the elements of the series can be infinitely increased or decreased, but they will never end. In this case, infinity is understood as the process of infinite extension.
In geometry, infinity is usually expressed as an infinitely extending area in a plane or space. For example, when we say that a plane is composed of an infinite number of points, it means that the points on this plane can be infinitely increased or decreased, but they will never end. In this case, infinity is understood as an infinitely extended space.
In calculus, infinity has two main forms: discrete infinity and continuous infinity. Discrete infinity means that elements in a set can be added or subtracted indefinitely, but they will never end. For example, we say that an integer set is infinite, because integers can increase or decrease indefinitely, but they will never end. Continuous infinity means that the elements in a set can be infinitely close to the distance between any two elements, but they can never reach the distance between these two elements. For example, we say that the set of real numbers is continuous and infinite, because real numbers can be infinitely close to the distance between any two real numbers, but they can never reach the distance between them.