Tableau Desktop
Backbone of product offering. Use Tableau Desktop to create your workbooks. As a Tableau developer you’re going to be spending 99% of your time using this tool.
Tableau Server
A secured intranet portal where users can easily publish and share their Tableau Workbooks by simply providing a link to a workbook. Does not require Tableau Desktop to consume the information, just a browser…and a Tableau Server user license of course (they can’t just give it away).
Tableau Online
Cloud based “Tableau Server” solution. Tableau will host your server, enabling you to easily scale and publish content right out the gate. Tableau Online handles the “keep the lights on” tasks, handling all maintenance and upgrades. You just focus on creating and sharing your Tableau Dashboards. As your user base grows, having an in house Tableau Server becomes much more cost effective.
Tableau Reader
Tableau Reader is a free tool that allows you to open, but not edit Tableau Workbooks. You can only “read” what others have created. This is a great option if you are just getting your feet wet in Tableau. Think of it like emailing a colleague an excel workbook in read only mode. Exact same concept (save for the ability to make edits). The major flaw with reader is the static nature of the workbook once it’s exported as it’s not editable/updatable. Security is also a big concern as Tableau Reader files can be opened by anyone with Reader installed.