Fasting Ramadan is one of the five pillars — named in the same breath as the testimony of faith, the five daily prayers, zakah, and Hajj, in the well-known hadith describing what Islam is built on. It became obligatory in the second year after the migration to Madinah, and it's binding on every Muslim who meets a short list of conditions.
You have to have reached puberty — bulugh — recognised by physical signs or, failing that, by age. You have to be of sound mind. You have to be physically able to fast without it seriously harming you. And you have to be at home, not travelling, since a journey brings its own allowance.
Outside those conditions, fasting simply doesn't apply, with no makeup required at all: young children who haven't reached puberty, and anyone who has lost their sanity. Encouraging children to practise fasting part of a day, building up gradually as they get older, is a good and recommended thing to do — but it's training, not obligation.
Then there's a separate group of people for whom fasting is temporarily set aside precisely because of real hardship — illness, travel, pregnancy, breastfeeding, the frailty of old age, the days of a woman's monthly cycle or the weeks following childbirth. Some of these are made up later, day for day; others are addressed differently. That's a genuinely separate topic with its own detail, and worth asking a knowledgeable teacher about directly rather than guessing at from general principle. What matters here is the shape of it: none of these allowances are loopholes to feel guilty about using. They're written into the obligation itself, by the same Lord who set the obligation in the first place.
What does this bring up for you today?
To carry with you
The Prophet ﷺ said Islam is built on five pillars — testifying to Allah alone, prayer, zakah, fasting Ramadan, and Hajj (Bukhari and Muslim). If you fall into one of the excused categories, take the allowance without guilt; it was placed there deliberately, not grudgingly.