Fora and forums are plurals of forum . The former conforms to the original Latin, which some people prefer, while others like the Anglicized form. Neither is right or wrong, and choosing between them is mostly a matter of preference. Be aware, however, that forums is by far the more common form in most types of writing throughout the English-speaking world. Fora still has the edge in scientific and scholarly contexts, though. This is not surprising, as Latin forms are typically more common in these types of writing. Outside these contexts, fora can be distracting and even confusing to readers who are used to seeing the English word.
Orthography refers to the study of letters and how they are used to express sounds and form words. The ’ in “penguin’s” is grammar as is the absence of a ’ in tits.