A: 4K â also known as UHD (more on this in the next answer!) â is a picture technology that quadruples the number of pixels found in a full HD picture. These pixels are usually arranged in a 3,840 x 2,160 configuration, compared with the 1920x1080 you get in a full HD TV.
Files with the .7z extension are very similar to Zip files. These files are compressed archive files, usually created by the 7-Zip file archive utility. 7Z files can make it easier to send files and folders over email and the Web.
I've used a lot of un-RAR tools and, in my opinion, the best is the free 7-Zip program. Note: Some RAR files are multipart files and are named something like 123.part1.rar, 123.part2.rar, etc. Those types of RAR files should also be able to open with the programs I mention below. How to Open RAR Files With 7-Zip.