Fasting

Fasting is the English word for 'sawum'. It's very imnportant to all muslims especially in Ramadan.
Fasting is not just not eating or drinking but  also our parts of our body must observe sawum.
Our eyes, ears and all other parts of our body. Here are a list of things that  invalidate the fast if done on purpose

1. Eating and drinking 
2. Saying false things to Allah, Prophet (s) or with the successors of the Holy Prophet(s). 
3. Making dust reach one's throat. 
4. Immersing one's head completely in water. 
5. Vomiting 

Wajib Fasts

1. Fast during the month of Ramadan of course 
2. Qaza fasts for the month of Ramadan 
3. Kaffara fasts 
4. Fast is broken or left out deliberately

Mustahab Fasts
On  all days of Rajab, Shaban or any possible month  to fast even it it's only a day or a week.

Haram Fasts

1. Eid-ul-Fitr
2. Eid-ul-Adha
3. Fasting during illness
4. Fasting when travelling before salatul Dhuhr. 

Makruh Fasts
It is Makruh to fast in Ashura.

A person is allowed to break his fast that is Mustahab if it is not Qaza before Salatul Dhuhr.