Just as in English we have 'they' and 'them' (but note, only 'you'),

In English, we have two forms of the third-person plural pronoun: "they" and "them". [Usually which one to use depends on whether it's the subject or the object, but sometimes we use the objective form as a so-called disjunctive or "stress(ed)" pronoun.] (However, note that we have only one form of "you".) Similarly, French has different pronoun forms, and in this lesson you'll learn about the use of so-called "stress(ed)" pronouns in French. [These are pronouns that are in the objective form and are often but not always used as objects. As "stress(ed)" pronouns they can also be used as the subject, or to repeat the subject for emphasis.]

That sentence isn't really worded to pull you into that lesson, I agree. It's difficult to wrap your head around. Aaron explained the use of stress pronouns already. I just wanted to draw your attention to their use in English:

You and me, we are going to have fun! -- Toi et moi on va s'amuser!

Here toi et moi are stress pronouns of what would otherwise be tu et je. It is exactly the same in English: you and me are also stress pronouns of would otherwise be you and I. Note, that the stressed version of you doesn't change but the stressed version of I is me in English.

You and they are going to have fun! -- Toi et eux vous allez vous amuser!

Same thing again, this time with eux being the stress pronoun for ils (and "them" being the stress pronoun for "they" in English).