What's the meaning of _AT_ attribute of a file?

Hi, everyone!

I entered the command 'ls -l' in a terminal. And some of the display was

-rwxr-xr-x@ 1 aaa staff 3.3M Feb 21 08:50 abc.exe
-rwxr-xr-x 1 aaa staff 17K Feb 11 19:11 xyz.exe

Both abc.exe and xyz.exe are executables. But I just don't understand the meaning of the @ sign on the first line. So can anyone explain this?

Thanks in advance!

if @ is the attribute marker, then it means it hasn't been archived since the last backup.