If you wanted to dictate a message using Gboard, you previously needed to be connected to the internet to do so. But what if there are times you aren't online and you want access to this feature. Or you'd rather not send out your voice data to Google? Well, Gboard is testing out offline voice typing. This video hows how it works and it seems to be working pretty well. Also, it doesn't take up that much space at 85MB. Google hasn't officially pushed this feature out so they might be working out some of its kinks.
Source: XDA Developers