The Food and Drug Administration (FDA) approved the first Covid vaccine -- from Pfizer-BioNTech -- in the summer of 2021. It later approved the Moderna vaccine in January of 2022. This means the vaccine received the standard Biologic License Application (BLA) approval, which represents the FDA’s highest standard and requires a longer period of evaluation.
The FDA had previously granted Emergency Use Authorization (EUA) to the Pfizer-BioNTech vaccine, the Moderna vaccine, and the Johnson & Johnson vaccine. Additional vaccines are in Phase 3 of clinical trials and maybe submitting data for review with the FDA soon.
Emergency Use Authorization exists to allow the FDA more flexibility to review and authorize products for use during public health emergencies, like a pandemic. In order to grant an EUA, the FDA must determine that a vaccine can effectively prevent infection or disease and that its benefits outweigh potential risks (like serious side effects). While the EUA allows people to start receiving the vaccine, vaccine developers will continue to submit data to the FDA to achieve full FDA approval through a BLA.