When I studied Latin in high school, I don't recall there being any
definite or indefinite articles (equivalent to the words 'the' and
'a').

However, modern romance languages such as French and Spanish DO have
definite and indefinite articles (e.g. le, la, un).

When and why were such things introduced to the romance languages?  I
bet there's an interesting store to be told.

Here's a tidbit:

"In the etymologies of many languages, definite articles formerly were
demonstrative pronouns or adjective; compare the fate of the Latin
demonstrative ille in the Romance languages, becoming French le, la
and les, Spanish el and la, and Italian il, lo and la."

http://en.wikipedia.org/wiki/Grammatical_article

There's some interesting material here:

http://www.geocities.com/email_theguy/rvulgar.htm