Microsoft Teams has 2 versions available, Free and Paid. The difference between the two are the features available. For example, the free version allows internal chat and audio/video calls (one-on-ones and groups). However, with the free version, it is not possible to schedule the audio/video call meetings, which the paid offers.
Microsoft 365 (formerly known as Office 365) may include the full version of Microsoft Teams. Here is a quick overview of the plans that include Microsoft Teams: