These are Google Earth (KMZ) files that can be displayed within your internet browser. These files link to Alaska airport data images that overlay on the Google Earth imagery. It is still under construction but there are quite a few airports already completed.
Caution- These airport images and data are only updated one per year or less and are not guaranteed to be error free. The data date on each airport is the effective date of the Supplement Alaska or Canada Flight Supplement from which the overlaid information is extracted. The date of the image will normally be different. If it is a Google Earth image, the date should be displayed in the lower left portion of the screen, perhaps depending on the version of Google Earth you are using. However, you will probably need to de-select the overlay images before that date appears. If the image is not a Google image, the photo date will appear on the photo itself, if available. Always verify the information found here with the current NOTAMs and Supplement Alaska, or Canada Flight Supplement as appropriate. Also be sure to delete any previous versions of the KMZ file that you may have saved in Google Earth so they do not continue to be displayed.