Tag spam would be putting popular, yet irrelevant tags on your post in an effort to get them more views. For instance, lets say you tagged your post about movies under the #food or #steemit categories despite your post having nothing to do with either of those.
Using irrelevant tags, especially popular tags, makes it hard to find good and relevant content.
We encourage people to try to use only relevant tags when posting.
Ah! I see, thank you - I read the tags obsessively to see where I might fit, so I think I will avoid this one. I get it now and that would totally annoy me. Thank you so much!