I always heard my lead says – Please get latest the solution i have refactor the xxx class/ oh must be my refactoring break the solution.

In short, code refactoring is a disciplined technique for restructuring an existing body of code, altering its internal structure without changing its external behavior, undertaken in order to improve some of the nonfunctional attributes of the software. Advantages include improved code readability and reduced complexity to improve the maintainability of the source code, as well as a more expressive internal architecture or object model to improve extensibility.
(Wikipedia always is my best teacher)