what does '$?' mean in a shell script?

Question

I came across a shell script that contains a statement like,

if [ $val -eq $? ]

What does $? mean here?

Answer 1

ls *.* or ls would produce the same result. Meaning show zero or more files with any extension in the current directory.

echo $? would display the exit status. If at least one file is displayed from the last command ,the exit status would be zero(success).