You said, "Forgiveness means if anybody do some harm to you you don't react and just try to pretend like it never happened to you."
This is called "Kshanti-paramita", the perfection of patience.
In Buddhism, patience does not mean that you put a lot of effort to keep yourself calm. In Buddhism, patience means you do not have attachments. Because you have no attachments, you can not be offended.
The biggest attachment is Ego, the feeling of self-significance in the world. When you feel you are significant, and people do something that shows that you are not, you can easily feel insulted and lose temper. So Ego is like a big sore, very sensitive, that makes you very vulnerable.
Other types of attachments are attachment to religion, attachment to "we", attachment to some sort of theory, attachment to intellect, attachment to purity etc.
When you have no attachments, no Ego, no self-significance - you become very patient. You become unmovable, invulnerable. This is called perfection of patience.