Understanding Field Update and "Repeat this workflow whenever a lead is edited"

Understanding Field Update and "Repeat this workflow whenever a lead is edited"

I have a workflow triggered on Field update

1. Does Field update only trigger when a field changes?

For example:
  1. if the field value is "dave" and is updated to "paul" it will trigger
  2. if the field value is "dave" and is updated to "dave" it will not trigger
At present, the action only fires once. 

2. Am I also correct that if I tick "Repeat this workflow whenever a lead is edited", it will only trigger on this record, on this field?