A watermark will not stop a determined thief. Software has been able to reconstruct what is behind a mark for years. What it does do is keep your name attached to work that travels, make casual reuse slightly awkward, and mark a proof so it cannot be mistaken for the final file. Those are real, and worth doing properly.
Batch Watermark takes a selection from the media library, a mark from your brand kit or an uploaded image, and applies it across all of them with the same position, size and opacity.
Position matters more than people think. A corner mark is conventional and crops off in two seconds. A mark placed slightly off center, overlapping the actual subject, cannot be removed by cropping without removing the reason the picture exists. For proofs, that is the right answer.
The setting to insist on is output. Write new files, never overwrite the originals. Batch operations run against the wrong folder more often than anyone admits, and an overwritten original is not recoverable.