When new software comes out it has a version number like 8.2.0. The software industry needed a standard way to describe software releases so we as consumers of the software could determine how big of a change it was and determine if we should upgrade.
Major versions are defined as a version where the package has made API changes that are incompatible with the previous major versions.
When we compare SemVer numbers it’s important to work our way left to right and treat each number as a number and not a string. For example version 0.3.10 is ordered before 0.10.3 because the major number is the same but minor 10 is greater than 3 and version 0.1.1 is ordered before 1.0.0 because 1 is greater than 0 in the major version and all others are unimportant.