Stephanie, an API call occurs when your course accesses the server. So in terms of the Data Cloud widget, whenever you call CloudSet(), CloudGet() or any other related function.

So in other words with my 5 fields it will in the data cloud it will add an API call for each time it sends one field to your server? Then on the Leaderboard widget it will count as an API call each time there is new data sent to the server? Will it also count as an API call each time the table is viewed?

Yes, if you send 5 fields, each one is its own API call, so you will end up with 5 calls.

The leaderboard count is separate. Writing a new row counts as one call, displaying the table does not count as a call.

The monthly free tier for Data Cloud is 100 calls, for Leaderboard -- 200 calls.