access, modify, change (file time)

Access Time | atime | -ult

This is the time that the file was last accessed, read or written to.

Modify Time | mtime | -lt

This is the last time the actual contents of the file were last modified.

Change Time | ctime | -cl

This is the time that the inode information (permissions, name, etc., the metadata, as it were) was last modified.