"The boy eats some sandwiches."
Translation:Il ragazzo mangia dei panini.
Okay so do the forms of "di" translate to possession (English version of 's) AND the measurement "some"
It's exactly the difference between "gli" and "i".
Keep in mind that the noun itself determines masculine vs feminine, singular vs plural. The specific form the article takes from there is determined by the word that comes immediately after the article.
i nostri elefanti
I got this wrong, put "degli panini" instead of"dei panini". I looked it up and when the following word starts with a vowel sound you need to use degli. Here the 'p' in panini simply gets dei. In more detail - this from the web: the rule is "Gli" goes with: "z, pn, gn, ps, x, y, s+cons and vowels"