Make contents of one dropdown dependent on the choice in the prior dropdown

How do I make it so contents of one dropdown will vary based on selection in the prior dropdown?

Also, How do I make it so a dropdown box has an option "other" and if that "other" option is chosen another textbox opens up allowing the user to type in a description for other?

Hi,

We have a widget for that: http://widgets.jotform.com/widget/dynamic_dropdowns

That's possible when you create hide/show condition.

Example:

Hope this helps!