how ./example.sh differs from . /example.sh and ./ example.sh

May i know the difference between the execution of the commands:
./example.sh
. /example.sh and
./ example.sh

the last and last but one is having space in between that is the difference please suggest me the answer for this...:confused:

The first one is correct if example.sh is in the current working directory.

The second one is correct if example.sh is in the root directory which is named /
AND you want to source the script (not run in a subshell) dot space scriptname:

.  myscript.sh 

is called sourcing a script

The third one is completely wrong in anyway I can think of.

and assuming that the file is executable and has a #! line at the beginning

Hello JIM,

Sorry for delay in response can you tell me what "source the script" means?????

Its answered here - link
Sourcing a script runs the script in the current shell. So, any changes made would be visible/available after its execution in the current shell.