What does it mean ??
Answers
n € N, which means "n" belongs to "N".
Take a real life example. You have a happy joint family which gives you joy more than enjoying with friends. So, you are ultimately a member of your family which indirectly states that you belongs to that (your) family.
Similarly, in the field of mathematics, when you are constructing (or, creating) groups, you have to pick out categories. Same categories will belong to [€] same group.
One more example you can take if it is still unclear to you. You had solved many "Find the odd-one-out" type questions in lower classes. For those type of questions, if there are a total of four options, three of them will belong to [€] the same category whereas the remaining one will be different and immediately, you can say that is the odd one which you now identified.
Behind all this, take a expression including example.
Fruits = {Apple, Mango, Banana, Grape)
From this above expression, what you can say?
You can immediately say now that
• Apple € Fruit group
• Mango € Fruit group
• Banana € Fruit group
• Grape € Fruit group
Clearly, "€" is read as "belong to".