Are file names in Ubuntu case sensitive?

I mean in windows if create a file named “a.txt” and trying to create another file in the same destination as “A.txt” is prohibited.

Is it same in Ubuntu?

Thank you for paying your valuable attention for a silly question.

To your title: Yes they are case-sensitive.

To your inline question: No, there is nothing that would prevent you from doing that.

Unix & Linux typically use case-sensitive filesystems, so there is a distinct difference between A.txt and a.txt.