From Lexicanum

Varga's Drop Legion is an Ork force during the Third War for Armageddon. They are specialist troops, and are sometimes known as tellyporta boyz because of the method they arrive in battle.

They were usually beamed into the midst of battles using the giant tellyportas mounted on the Roks in orbit, disorienting the Imperials who were fighting them. Often however the tellyportas didn't work correctly, and Orks would appear on the wrong side of the planet, or miles in the sky. This made it an unpopular method of transport, but it was very effective when it worked. They are generally formed of boyz and Nobz who the Warboss doesn't like much.

Sources

Armageddon Website