• Drivers made by NVIDIA, often just called nvidia. These are available free of charge to users, but they are not FOSS (Free, Open-Source Software).
• Drivers made by the free software community, called nouveau
Since Fedora has a focus on providing free software, the nouveau driver is what is included and used by default. The nvidia driver can provide better performance and more features. This driver can be installed by users who need either of those. If the default setup seems to work good enough, though, it is not necessary to switch drivers.