Forerunner's real name is Viza'Aziv.
So far the abilities she has showcased include super speed, super strength, and invulnerability. The Forerunners are all bred with a special protocol that prevents them from harming a Monitor.
Apparently, the Forerunner planet suffered from a interplanetary war against the Nine Houses (the civilizations established on the other planets in the solar system). It is unclear exactly how, but it seems that the Monitors saved the race from the threat, and formed a pact with the Forerunners. The Forerunner was the first recruit in Monarch's Monitor-destroying army. She did most of the leg work, recruiting key members to Monarch's cause, but when the battle royal of Countdown: Arena began, Monarch booted her from his team.
There are no male Forerunners, because Viza is the last left of her kind. This was explained in Countdown to Adventure #1. The monitors basically used them as an experiment to create the perfect fighting machines. Then they realized the Forerunners posed too great a threat, and annihilated them using Dark Angel and Shadow Demons.
Current Status: She and her crew helped save a baby planet from being destroyed. She used her blood to help the planet create anti-bodies to fight off the invasion. The planet is not Viza's and is using her genetic code to populate itself. We now have a Forerunner World #2, with Viza as the "thought mother".