Copy some data from one table to another in sql server 2012

Hello,

I have two existing tables: Table 1 and Table2.

Both tables have some data.

So I want to copy some data from one table to another not all and if both data are similar in both tables then I just want to replace that data not copy. I want exact output not more than that.

In Table 1, I have 20373 rows and In Table 2, I have 3545 rows.

So I just want to copy that rows which are not included in Table2.

Does it possible to copy some data from one table to another?How?

Now I am giving you my live example:

We are using Jenzabar ERP. In that front end side in advising tab we couldn't populate data. And after some research I found that advising tab is depend on student division tab. That means when someone fill advisor information in student division tab it will automatically reflect to advising tab but for some reason it's not working. So I just...