Every few months, the HERE Maps team (still part of Nokia for the long haul) produce updates to the core maps databases - the ones you access online or, more appositely, download for offline use. If you've previously downloaded a map (or multiple maps for countries) then see below for the steps to check for, and download/install, the update.

1. Start HERE Maps on your Windows Phone
2. Use the '...' menu to access 'download maps'
3. Tap on 'update current maps'. Updates will be shown for any countries you've previously downloaded
4. Tap on 'install'

The new maps seem to be a fairly complete set of data, i.e. not a small patch, so consider this a major Maps update.

If you've ever driven up a road and found that it had been changed in a major way without your traditional sat-nav knowing about it then be happy that your Windows Phone's maps are being kept bang up to date!