The x indicates a file is executable (or a directory is accessible) by the Owner, Group or 'Others' depending where in the permission string the 'x' is.
The s in the owner permissions execute field indicates the 'setuid' bit has been set (it allows a user process to 'execute' the file as if they were the owner, ie have the owner's (usually root) permissions).
The s in the group permissions execute field indicates the 'setgid' bit has been set (it allows a user process to 'execute' the file as if they were in the group, ie have the group's permissions).
If the s (in owner) is capitalised (ie S), it means that the 'setuid' bit has been set but the ordinary owner permission 'x' has been denied.
If the s (in group) is changed to l (lowercase EL), it means that the 'setgid' bit has been set but the ordinary group permission 'x' has been denied.
The t indicates that the 'sticky bit' has been set (most often seen on /tmp directory) which allows anyone to write files in the directory, but prevents files being deleted by anyone but the owner (and root).
I hope that helps.
Mike