Here’s a primer based on my own understanding. Anyone can feel free to correct if I mess something up and I can edit my post, I’m not a Muslim myself:

• Ramadan is a month on the Islamic calendar (I think the ninth one?).

• one of the pillars of Islam is that during Ramadan, Muslims need to fast from food and drink while the sun is up. Other pillars are things like praying five times a day, going on pilgrimage to Mecca, and donating a portion of your wealth annually. So it’s no exaggeration to say that Ramadan is extremely important to Muslims.

• I believe the rationale for Ramadan is that it is an observance of Mohammed’s revelation.

• there are exceptions to fasting requirements. Off the top of my head are people who are sick, women on their period, and if it would put yourself at serious risk of harm by fasting.

• Muslims use a lunar calendar (measures months by looking at the phases of the moon). Because the moon phases and procession of the earth around the sun are not in sync, this means the months on the Islamic calendar don’t line up with the seasons. So Ramadan can be in the winter or summer on certain years, and therefore sun up/sun down times can change.