Smurfchops: The reason for using private browsing is so that no-one can see browsing history. This won't stop your employer from knowing where you have browsed however if you're on a private network (at home for instance) then it means that anyone (friends/family) that has access to said device can't look at your browsing history.
The downside is that if you've been searching through pages and you forget the site URL then you can't go through your history to try and find it.
Those are the benefits and downsides to private browsing.