I am new to Android, and would like to know whether it is possible to add a desktop shortcut so that when I press it, I can send an email to a specific person, and I just need to put the subject and send it.
Not for a specific person -- but still a shortcut, which simply opens the "compose new mail" screen: Compose Mail Shortcut. There's also Send Mail Shortcut which, from the name, sounds to exactly fit your purpose -- but as it helds no description at all, it's hard to tell. Last but not least: Mail Linker even seems to fit right from its description.
Unfortunately, as already mentioned, there's no such thing provided by the Android core system by default.
I don't believe there's anything built in to do that, but an app like Mail Widget will allow that.
For anyone looking for this, the Email Yourself app does this. Contrary to what the name suggests, you can also use it to create shortcuts to send emails to other people or groups of people.
The "Contact" widget allows you to add a shortcut to a specific contact on your Home Screen. Once you visualize the contact, you just have to click on his/her email address to send the email.
This is not exactly what you asked as it requires an additional step, however it's a feature available on all Android versions without requiring installing any external app.