Who is Porus from The Campaigns of Alexander and what is their importance?

Porus fought against Alexander at the Hydaspes River. Alexander split his troops and crossed a good portion of them. When Porus heard of the crossing, he sent his son out to engage Alexander, and then followed with his main force. The Macedonians killed his son, and when they engaged his main force, the Macedonians encountered Porus' elephants, who proved deadly to both sides. After Alexander effectively defeated Porus' forces, he asked Porus what he wanted. Porus replied that he wanted to be treated as a king should be. In return, Alexander gave Porus back his kingdom out of admiration.