Find The Value of one column in another colum

Hello,
I want to check what are the elements from a column that exists in columns(Previously containing rows) and what are the elements that are new to the column. what Excel formula i can use for that. Or is any shortcut method present for this.

Desc:
Column A contains 50 rows of element with heading NAME . Now In comes a new Set of NAMES containing 6 rows.
Now i want to know which all of these 6 new rows are present previously in Column A (NAME) and which all are new in the column B (NAMES).
Whichever element is new in column B(NAMES) copy those element into column A(NAME).