How do I find a field ID, either in Content Editor or Sitecore Rocks?

I am going through the 8.2 SXD training.

Chapter 11 is about Indexing and searching.

I am trying to create a custom index, and the instructions say to add the Field ID of 3 fields, one is from my template and two are from a base template.

How do I find the field ID?


Also, in Sitecore Rocks, when I hover over my template, I get two ID's:

ID: xxx

Template ID: yyy

For a template, what's the difference?