Cross object formula

1. When ever we want to show the parent record on child object  then we use the concept of cross object formula
2. With the help of formula field we can create a cross object formula
3. It is opposite of roll up summary
4. It refer another field reference    [ account.email ]
5. It can not use in another custom formula field but formula field can be use in another formula field
6. It by pass the sharing & security setting
   EX- like if you have private OWD on account object but you want to show the account email 's record on contact  object then we can get it with the help of the cross object formula.
7. Cross object formula can not refer roll up summary field
8. It can access custom formula field
9. Formula field contains up to  10 level object references and now  it is increased up to 15   (called spanning relation )
EX:
       [ obj1__r.name+obj1__r.name+obj2__r.name+obj3__r.name+obj4__r.name+ .......obj10__r.name ]
10. If any object have self lookup then it will count as another object
11. In the Formula Field's characters limit is  (3900).
12. There is a no limit of formula fields it same as normal field like [500]