Qual a diferença entre ./ e sh?

sh ls

sh nome_do_script

bash-3.1$ sh ls
ls: ls: cannot execute binary file
bash-3.1$

$ cat .

cat: .: Is a directory

`.    (a period)'

          . FILENAME [ARGUMENTS]

     Read and execute commands from the FILENAME argument in the

     current shell context.  If FILENAME does not contain a slash, the

     `PATH' variable is used to find FILENAME.  When Bash is not in

     POSIX mode, the current directory is searched if FILENAME is not

     found in `$PATH'.  If any ARGUMENTS are supplied, they become the

     positional parameters when FILENAME is executed.  Otherwise the

     positional parameters are unchanged.  The return status is the

     exit status of the last command executed, or zero if no commands

     are executed.  If FILENAME is not found, or cannot be read, the

     return status is non-zero.  This builtin is equivalent to `source'.

Read and execute commands from the FILENAME argument in the current shell context. (...) This builtin is equivalent to `source'.

$ echo 'echo oi' > script.sh

$ ./script.sh

-sh: ./script.sh: Permission denied

$ . ./script.sh

oi

$ source ./script.sh

oi

$