1. what does the program/module/class/method do?
2. what is its input, if any?
3. what is its output, if any?
for a class, understanding its lifecycle is crucial:
1. how is it created? by who? from a factory? what are the parameters required to create it?
2. does it have any enforced lifecycle methods? e.g. initialize, dispose..., who is responsible to call these methods, in which order?
3. what it can do at each stage of its lifecycle?
4. who is going to use it/what is its client?