Attribution
Attribution just means crediting an author, as in a byline:
e.g. "My Struggle Against the Trolls by Jimbo Wales"
The Creative Commons consortium refers to parametric licenses that require attribution as "by-", so the "by-sa" license requires both attribution and share-alike terms. The GFDL license requires the five most prominent authors to be credited so it too has an attribution requirement.
- Due to Wikimedia corruption and Mediawiki deficiencies (likely related) the Wikimedia usurpers do not recognize this legal requirement but instead rely on their GodKing's assertion that "everything is ok" and no legal trouble will result. That GodKing is not a lawyer, however, so this belief in his opinion is only groupthink, and probably quite dangerous.
Trolls seem to think that any attribution interferes with the free circulation of fiction, and that usurpers and Wikimedia corruption prevent sharealike use that would make all large public wikis equal. For instance, they promote interwiki link standards that do not put any one source at the centre of the universe, and strongly oppose GodKings on all wikis. This is just one more issue in wiki governance.