By default Webhook To Jenkins for Bitbucket notifies Jenkins on all git reference changes, pull requests creations and re-openings. If users would like to limit which of these events trigger Jenkins, they can do the following.

Go to Advanced Configuration > Limit Events and select which events you'd like to disable. Each event thats disabled will be highlighted in red.

Here's an explanation of each event:

Pull Request OpenedIs fired whenever a pull request is opened.
Pull Request ReOpenedIs fired whenever a declined pull request is re-opened again.
Pull Request MergedIs fired after a pull request is merged
Open Pull Request Refs ChangedIs fired when change happens to any git reference which is a base branch of at least one active Pull Request. This includes commits, pushes, edits, branch creations and more. Note, we filter out all reference deleted events. Doesn't fire when refs are modified in forked repository in back-merge Pull Request.
Non-Pull Request Refs ChangedThe same as previous, but triggered for changes in references which do not participate in any active Pull Request.

You can also hover on event name on configuration dialog to get quick in-place event description.