Some are case-sensitive, some are not. Linux is case-sensitive, OSX is not.
https://apple.stackexchange.com/questions/22297/is-bash-in-osx-case-insensitive
ext ext2 - addressed issues of inode immutability and fragmentation ext3 - added journaling which helped crash recovery ext4 - backward-compatible with ext2 and ext3, added journal checksumming