So, why exactly does ./executable work in Linux and Unix (and .\ in windows)?
The ./ translates to: in the current directory (dot(.) : this, slash(/) : directory)
Now recall that there is a variable called $PATH in all operating system shells.
The role of this variable is to store the path to all the places where system binaries are stored (for eg in /bin or /usr/bin or /sbin)
Also remember that shells can then take these binaries as inputs and directly run them like
ls
cd
python
chmod
When you have an executable that does not exist in this path, and you want to run, what must you do then? 🧐
./ ofc!
In this way, we specify the complete path to the executable, and hence can run it directly
.executable does not work because it is a valid directory name.
/executable does not work because it can mean the root/executable and hence we need ./