Does update tag -> tag2 in a BUR keep its category?

How is it different from alias tag -> tag2?

Lance_Armstrong said:
Does update tag -> tag2 in a BUR keep its category?

How is it different from alias tag -> tag2?

1. Not sure

2. An update is a one-time change (all current uses of tag will be changed to tag2, but you can still add tag to posts afterward), while an alias changes all current and future uses.