It will overwrite the tree on remote as long as remote hasn't changed since you last fetched it. Like --force, but can help to prevent overwriting other people's changes when they push in between you fetching. It doesn't always work, particularly if you have a tool which continuously fetches remote, like an IDE configured to do so such as VSCode. In that case, you will have fetched the other person's changes, and --force-with-lease will happily blow-away anything on remote that might not be in your tree yet.