A merge is the act of combining changes from one line of development into another. Two developers (or one developer working on two features) each make edits in isolation, and merging brings those separate edits back together into a single, unified version of the code.
Picture two editors revising the same book chapter on their own copies. One fixes the intro, the other rewrites the ending. Merging is the editor who lays both copies side by side and produces the final version that keeps both improvements. Usually this is automatic, because the changes touch different parts. When both people edited the exact same sentence, you get a conflict that a human has to resolve by hand.
Merging is a core part of working with Git, where each feature lives on its own branch until it is ready. The merge is the moment that finished work rejoins the main codebase, and on a healthy team it only happens after a review and a green test run.
Timing matters more than people expect. A branch that sits untouched for three weeks drifts further from the main code every day, so its eventual merge tends to be the painful one full of conflicts. The fix is not a clever tool but a habit: pull the latest main into your branch often, and merge your own work back while it is still small. On platforms like GitHub this is also where automated checks earn their keep, blocking a merge until the tests pass so a broken change never lands quietly.
At TopDevs we keep merges small and frequent, which means fewer conflicts and far less chance of a surprise breaking your project.
