Those adventurous enough to take the first public betas of iOS 11 and macOS "High Sierra" for a spin can now upgrade to the second beta builds of these upcoming operating systems by Apple. Since both releases come less than three weeks after the first betas for the public, there are no big changes.
As it usually happens to minor updates for the public beta releases, there should be quite a few bug fixes involved, next to various minor improvements and performance tweaks. Both macOS 10.13 "High Sierra" and iOS 11 were unveiled during WWDC 2017, and their final builds should become available later this year, most likely by the end of September.
Since these new betas are still quite far from the reliability of a final product, one needs to be careful when installing them. In most cases, it is good to have a backup device to install them on since nobody recommends running beta operating systems on the hardware one relies on.