Subscriptions are contractual agreements between you (the customer) and us (the provider) to provide various services and resources for a payment in advance.
Subscription are divided into plans (levels) each with a different price and providing different service restrictions and number of available resources.
Using up the provided (by your current subscription plan) number of resources will prevent your from creating any additional ones until you upgrade your subscription.
To view your current and past subscriptions click on Subscriptions in the navigation menu on the left.
You'll see a list of all of your subscriptions along with your currently active one at the top of the list.
Click on the name of each subscription to view its details, or the gearbox icon for additional options.