An indicia is a strip of information in periodicals which is both a legal notice and a legal requirement in many countries. It establishes the name that will be used for copyrighting the contents of that publication. It also provides the address of the publisher and the actual publication date, which can differ from the date on the cover of the magazine, if any.
For the purposes of naming a periodical, the name given on the indicia is generally considered to be the most "correct" name, superseding even the title on the cover, as it is sometimes unclear which words on the cover of a magazine are meant to be the title.
In the example below, drawn from the first issue of the story, Ripper's Curse, we can see that the name of the publication is simply Doctor Who #2.
By convention, if there are multiple publications with the same indicia name, then they are distinguished by the year in which issue #1 was published. Hence, there are Doctor Who (1984), Doctor Who (2008), Doctor Who (2009) and Doctor Who (2011).