What are tags, observation fields, and annotations?

On the lower right-hand side of any observation page, you'll see a section called Annotations, alongside Projects, Observation Fields, and Tags.

Tags are short pieces of text that can be attached to observations to aid in searching. They can be any text string, and only the observer can add them to their own observations. They can be used to search for observations in the Explore page, using the "Description / Tags" filter. 

Projects are groups of observations with a common purpose. Anyone can create projects and add any observations to them (unless the observer has opted out). Projects are recommended for community building, rather than just tracking observations. Read more about Projects here.

Observation Fields have names (such as "Eating") and allowed values (such as a taxon). The values have types such as numeric, text, dates, and taxa. Text fields can include any arbitrary user-entered string, or they can be restricted to predefined values. Anyone can add observation fields to any observation (unless the observer has opted out). Often, observation fields are associated with a particular project seeking to gather additional metadata associated with observations. Existing observation fields can be reused or anyone can create new observation fields - they're not regulated. You can search for and create Observation Fields here.

Annotations are name/value pairs like Observation Fields, but the names and values are controlled by iNaturalist staff. This is to avoid the duplication and confusion that happens with observation fields resulting from their many different creators and uses. At present, Annotations exist for Life Stage, Plant Phenology, Alive or Dead, and Sex. We anticipate adding more. See the current list of Annotations here.