Eating kosher is essentially three levels of paying attention to what you eat.
1) What you're actually eating. There are prohibited animals that can't be eaten. Everyone knows pig, but I also don't eat shellfish, shrimp, or bottom-feeder fish like catfish. There's also shark, swordfish, and insects.
2) What you're eating that item with. I don't eat meat with dairy. This even includes meat with a side dish that has dairy, such as a steak eaten with a baked potato with butter and/or sour cream.
3) How you prepared it. Going back to what you eat the food with, I wouldn't eat a steak cooked in butter. But more than that, I have two sets of kitchen supplies, one for meat and one for dairy, so that I don't accidentally mix the two. Surprisingly, if you cook chicken soup in a pot one night and clean it well afterwards, and then boil water in it the next day, a professional chef could tell you what you cooked! Meat and dairy could be absorbed into the pot or plate or other utensil, so we separate them. That means I use pots, pans, silverware, and dishes that are designated as either meat or dairy. I don't use other peoples' dishes and pots because they've probably been used for both.
If the person is still interested and has more time, I spend a minute or two on each topic, fleshing it out. Usually, they jump right to questions about specific examples.