Ramadan Fasting is fardh(obligatory,compulsory)for adult Muslims,except those who have been  exempted for one reason or another.

Exempted categories:
In Islam, people who fall under following categories are exempted from fasting in the month of Ramadan,

•Mentally challenged: Those people who are mentally challenged are not required to fast during the month of Ramadan.

•Children: Fasting during the month of Ramadan is not obligatory for children (those who have not undergone puberty).

•Women: Those who are passing from their monthly cycles. Or those who are undergoing the phase of post-childbirth. Women, in such conditions are exempted from fasting and are required to compensate for the missed days afterwards.

•Travelers: Travelers are exempted from fasting. Traveling is something you’re your culture considers as a travel. For example, going to university is not a travel that can exempt you from fasting. However, if you have to travel far and the journey is difficult then you are eligible for this exemption.

•Sickness: By Sickness it means, that when you are suffering from some ailment; if you fast your ailment worsens. Such types of sickness will implement this exemption from fasting. However, here it does not means that one needs to be sick deathly! It just means that if your disease or sickness may get worse from fasting, you are allowed not to fast during that period.

•Temporary sickness: These types of sickness include fever; moderate cough etc. These people are exempted from fast, and later they are required to compensate for the lost days.

•Permanent sickness: This type of sickness includes cancer, diabetes, AIDS, tuberculosis (TB); etc. These people are exempted from fasting but are required to give food to a poor daily during Ramadan. These people do not have to compensate for the missed days by fasting later, because of the permanent nature of the sickness.
A permanent sickness can also mean one who is very old and weak

•Pregnant and breastfeeding women:
Pregnant Muslim women who fast during Ramadan are likely to have smaller babies who will be more prone to learning disabilities in adulthood, according to new research. Muslim sisters, realize firstly that just because you’re pregnant or breastfeeding doesn’t get you off the hook. Only if you feel that the fast will make it difficult on you or that a Muslim reputable doctor tells you that the fast will have adverse consequences on you or your child, then you’re exempt from the fasting. There is difference of opinion on whether they should feed someone or if they should make it up for that missed fast.

Compensatory ways:
°Fast later in other months or after the month of Ramadan, as soon as the cause of delay is gone.
• Give a meal for each missed day of fasting. Or calculate the missed days and give all meals (according to the calculated missed days) together.
• You can feed various people or you can feed that compensatory meal to one person only.
• You can also give money to the poor that may buy them a proper meal. Best is to give food.

Type of food to give as compensation:
 °Give the poor a regular meal or a proper meal to eat.
• Meaning of ‘regular meal’ varies from culture to culture.
• If chicken is a regular meal for you, you should give that.
• But if that is a luxury for you then you are not obliged to give that.
• You may also give lentils, bread etc.

https://kapital929.fm/ramadan-people-exempted-fasting-holy-month/