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.
A file with the 7Z file extension is a 7-Zip Compressed file. Other types of files may also use the 7Z file extension. If you know of any additional file formats that use the .7Z extension, please let me know so I can update this information.
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.