In a Single Choice question respondent chooses one of the options you have given. The Single Choice question gives you exact number of respondents who choose a certain option in this question. Typical Single Choice questions include Gender, Age Group, Location, etc. Basically it can be used when ever options can be listed.
Hint:
If you have a really long list of options you might want to use a Dropdown question instead - there is a Search function in a Dropdown question type.