What is difference among Single, SingleOrDefault, First and FirstOrDefault?

Single – It returns a single specific element from a collection of elements if element match found. An exception is thrown, if none or more than one match found for that element in the collection.
SingleOrDefault – It returns a single specific element from a collection of elements if element match found. An exception is thrown, if more than one match found for that element in the collection. A default value is returned, if no match is found for that element in the collection.
First – It returns first specific element from a collection of elements if one or more than one match found for that element. An exception is thrown, if no match is found for that element in the collection.
FirstOrDefault – It returns first specific element from a collection of elements if one or more than one match found for that element. A default value is returned, if no match is found for that element in the collection.