When you use TaxonWorks you and your collaborators will likely want to take advantage of accessing and serving your data via the API(s).
An API is an application programing interface
Technically there are many APIs in TaxonWorks, however when we use the word in the context of TaxonWorks we almost always are doing so in reference to the functionality that lets you access your data outside the user-interfaces.
Very simply, the API lets you make a query on your data (and other's that have made it accessible), and returns you a response. It gives you "behind-the-scenes' access to the data the user interfaces are managing.
The API is currently documented here.