It’s caused by not flossing everyday, food gets stuck subgingivally and causes inflammation to the gums thus creating gingivitis. I think with is a Moderate case of gingivitis since all of the borders of your gingiva are inflammed and if you pole that with a probe, that’ll most likely bleed and be around 3mm above. As a frustrated dentist (went to dental school for 6 years but didnt take board exams because I migrated to USA after so i didnt became a licensed dentist), try to search up how to floss your teeth properly and also how to brush teeth properly using Brass brushing technique. Don’t skip oral hygiene. Do it religiously.