Abbreviation for "also known as," useful when defining terms that are known under two or more names:
Shortwave radio, a/k/a
World Band radio; or
Taiwan a/k/a Formosa.
Also pseudonyms vis-a-vis
Victoria Beckham a/k/a Victoria Adams and Posh Spice.
A simplified use has more recently emerged: simply to type the letters. omitting the slash
es (a/k/a "virgules") in between -- it is rare that anyone would confuse "aka" with a word called something like "akk-uh" and "aka" is easier to type:
David Johansen aka
Reginald Dwight aka Elton John.
But both spellings are currently in use:
Do you have any biographical information about writer George Orwell, a/k/a (or aka) Eric Blair?
Although an abbreviation, note that no period is required.