Koreans use the honorific when they speak to stranger or older than themselves. Using the honorific is very important in Korea because it can be very rude without using the honorific. I am sure that you can use your foreigner card for a while, but it will not work for everyone in Korea. To give your positive impression to people you meet for the first time in Korea, you have to learn honorific. At least, you need to know all greeting in honorific form.  For instance, 이름/name is 성함 in honorific.  Let’s compare informal and formal languages and sentences.

Hi/Hello.                         안녕 –> 안녕하세요

Good bye (to people who stay)    잘 있어 –> 안녕히 계세요.

Good bye (to people who leave) 잘 가 –>   안녕히 가세요.

What is your name?      이름이 뭐예요? –> 성함이 어떻게 되세요?

What is your job?          무슨 일 해요? –> 무슨 일 하세요?

Where are you from?   어디서 왔어요? –> 어디서 오셨어요?

Where do you live?         어디서 살아요? –> 어디서 사세요?

Where do you work?     어디서 일해요? –> 어디서 일 하세요?

As you see above the examples using (으)세요 is at the end can be very polite way to speak Korean. Please watch below the video to hear more explanation.