The order of Instagram stories means that the ones that were shared most recently are displayed at the beginning. This helps you catch up on the latest happenings quickly. However, Instagram's algorithm might also factor in your interests and relationships to prioritize certain stories for you.
The order of Instagram stories basically depends on when they were posted. The newer ones come first, so you see the latest content right away. Sometimes, it might also be affected by your interaction with the accounts, like if you frequently view someone's stories, they might show up higher.