What does Changelog mean?
A changelog is a record of changes to a software project or other technology product. This type of record has its own format for various types of projects, but is generally useful in showing when and why changes were made, and who made them.
Techopedia explains Changelog
A changelog plays a role in error control and debugging, software release and other project phases. Certain types of changelogs are maintained for various kinds of projects -- for instance, there is a typical convention for changelogs for Wikipedia entries.
Other standards for changelogs come from groups like GNU, a group supporting a UNIX-type operating system and holding certain kinds of software licenses, including for commonly used open source products.
Part of the philosophy behind changelogs and other kinds of documentation is that for larger projects, there are numerous people working on systems with different ideas about design and different kinds of awareness about standards and compliance.
That will lead to radically different techniques, and the more these are documented, the more people can work together. However, some developers also consider a detailed changelog to be excessive, and question whether it really provides value to either a team or an end-user.