Din/Dit/Dine is when you're speaking to one person, jeres is when you're speaking to more than one, or about something that a group owns if you're speaking to a person from that group. For example: Jeg elsker din hund = I love your dog (either it's only this person's dog or you don't know someone else also owns them)
Jeg elsker jeres hund = I love your dog (You might be speaking to the multiple people who own the dog or speaking someone from the family and know they are part of the family/it's come up in conversation.
Think of the difference like the difference between "your" and "y'all's" in colloquial southern US English
I love this Danish course so much, as well as the people here, really... Most are usually so good-humoured and polite - the comments never fail to amuse and teach us.
(off-topic/random, I know, but worth mentioning it, since it's been utterly hard for me to actually enjoy anything all)