How do I use a set in Salesforce?

How to use Set in Salesforce

1. Syntax:
2. Creating a set: Set<DataType> variable name=new Set<DataType>(); ...
3. add(SetElement): It inserts an element into the Set. ...
4. addAll(fromlist|fromset): It inserts list of elements or set of elements into the set.
5. remove(Element): It deletes the element from the set.
6. removeAll(List|Set): ...
7. contains(Element): ...
8. size():