I see misunderstanding of tags too often on this board.
Maybe the word 'ID' or 'key' would be better.
A tag is like:
- an identifier
- an effigy
- a driver's license number
- a license plate number
To treat an identifier as if it were the thing it purports to identify is akin to practicing voodoo, pushing pins into dolls wearing the faces , hair, and fingernails of your enemies.
https://www.google.com/search?q=this+is+not+a+pipe
AI2 tags and values chapter:
http://www.appinventor.org/bookChapters/chapter22.pdf