How do these 3 tags differ?
There are 15 questions tagged with the first two, among which two are mine. Note that I initially tagged mine just
identify-this; someone else added the
Have you tried clicking the tags? The wikis seem to answer your question perfectly clearly
locate-this: You know the name of a cafe, a church, etc. but you don't know where it is. Help!
identify-this: Finding the name of some place, food, monument, or other travel-related thing.
where-on-earth: For questions about location of specific place or location of longest/highest/biggest/the most... place/thing on Earth