That means you can sell items you find for Platinum and use that to buy things from the premium cash store. It's up to you to find a purpose in Warframe.
Warframe doesn't really have raids like you would see in Destiny 2, though there is extremely challenging group content. Other players partake in 'fashionframe' and customize their warframe's appearance to stand out from the crowd. Some players try to collect every warframe, some will stick to a few and work on making them as powerful as possible. That said, Warframe also differs from MMOs in several key areas:
