As of right now, and based on the number system for Apple’s updates, this appears to be a minor software upgrade. It will likely aim to fix any issues that have been discovered in the last public update, iOS 11.2.1, as well as aim to improve performance and other tweaks. It is not likely that this software update will include any major forward-facing features for the end user, but if anything like that is discovered, we will update this post accordingly.
If you’ve signed up for Apple Beta Software Program at beta.apple.com and have enrolled your iPhone, iPad and Apple TV, you can download the new betas via the Software Update mechanism (your devices must have a proper Apple certificate).
iOS 11.2.5 and tvOS 11.2.5 are bug-fix updates with no new features.