Clitics is just a fancy name (from linguistics) that DL sees fit to use for unstressed object pronouns - direct (DO) and indirect (IO). In English DO and IO pronouns are the same:
"She loves him " - him = DO
"She gave him a kiss" - him = to him = IO
In Romance languages DO and IO tend to be the same for 1st and 2nd persons - me, te, nos etc, but differ in 3rd person, for example o, a (DO), lhe (IO).
Romance languages also have a third form of pronoun known as tonic pronouns, used after prepositions and for emphasis - (para) mim, ti, ele, ela, nós, vóces, eles,elas. Note that in 3rd person they are the same as subject forms.
Incidentally, no standard Romance language courses for foreign learners that I have come across use the term clitic. Is it just DL being a bit pretentious, I wonder.
To find out more just google "object pronouns in Portuguese". This site gives a fairly detailed account for English speakers:
I'm curious... I also thought that this could be translated to "You know I love you [voces]", but wouldn't:
"You know I love you [voces]" ---> "Voces sabem que eu lhas amo"
Or is "lhas" not even a word? I figure "lhe"= "to him/her/you", "lhes"="to them", then perhaps there's a "lhas/lhos"?
Yes, there is, but only if you have lhe+os or lhe+as, there is also a lho and lha contraction for lhe+o and lhe+a, I think it´s like "Você da lhes os livros"- "Sim, eu lhos dou." But to discuss the "You know I love you!"- question: It´s not that unlikely that you speak to a group of women, so why are they saying that it´s wrong?