Q: also which one is it that comes wit mac
A: Case sensitive allows files of the same name but some difference in letter case to be in the same directory ("folder"). The standard format from Apple is not case sensitive. For example, in the standard format, "Mac OS Extended (journaled)", a file named "filename.txt" would be identified exactly the same as "fileName.txt" so the two must be in different directories. With the "case sensitive" format, they are seen as different files. Some third-party applications are not designed for the case sensitive format so they may not always perform correctly. Unless you have a pressing need to save or locate files based on letter case, stick with the non-case sensitive option. You can verify which format has been used with your drive volume (that means a drive or a partition of a drive), by selecting it in a Finder window and apply the "Get Info" command, such as command + I or File > Get Info. The format type is listed in that Info window under "General".