The second method of script execution is implicit, which involves just typing the name of the script file itself, as in:
$ bashfile $ perlfile
Being able to run a script implicitly involves a little more work beforehand, since you have to:
place a valid interpreter line at the top of the file
grant appropriate read and execute access to the file
make sure the script file is in your search path. (If it isn't, you can still run the script implicitly by giving its full address, as in:
$ /home/fred/bin/bashfile $ ./perlfile
It should be obvious that running scripts implicitly is more convenient - it just takes a little more time to set them up that way.