The standard Java libraries fail to provide enough methods for
manipulation of its core classes. The Commons Lang Component provides
these extra methods.
The Commons Lang Component provides a host of helper utilities for the
java.lang API, notably String manipulation methods, basic numerical
methods, object reflection, creation and serialization, and System
properties. Additionally it contains an inheritable enum type, an
exception structure that supports multiple types of nested-Exceptions
and a series of utilities dedicated to help with building methods, such
as hashCode, toString and equals.

With version of commons-lang 3.x, developers decided to change API and
therefore created differently named artifact and jar files. This is
the new version, while apache-commons-lang is the compatibility
package.