I am new to concrete5
.
I want to edit the email template which is sent to the customer email id in the forgot password section.
Where do I find the controller function, if the url is www.mydomain.com/login/password_sent/ ?
Standard email content is taken from proformas in /concrete/mail/. In your case, from /concrete/mail/forgot_password.php.
Rather than edit the actual file, you should create an override by copying it up to /mail/forgot_password.php and editing the file there.
The concrete5 core will then use the override copy of the file instead of the core file.