Welcome Tenno, a long time ago Warframe Universe evolved radically. I still remember that moment when I put my feet for the first time in the Plains of Eidolon. There were hard times, but also full of Quests and challenges to face and overcome.
Here you will find the different open worlds in Warframe. In each one of them you will see the starting point of each open world and an index to make your first steps easy. Do not fear and go for it.
And that’s all we can tell about the Open Worlds in Warframe. As new one appear you can find them here. Remember it and make all Tenno in the Origin System know it.
Good luck out there, Tenno.