(Grammar) -세요, -으세요, 같이 and 누구

-세요 is an honorific imperative ending (still remember?). It follows verb roots ending with a vowel.

• 오세요. Come here please.
• 들어오세요 Come in please.
• 어서 오세요 Come on in please.

-으세요 is the same meaning as -세요. But -으세요 follows verb roots ending with a consonat.

• 넣으세요 Put it in please.
• 앉으세요 Have a seat please.
• 읽으세요 Read it please.

같이 (sound is Kachi) is means together.

• 같이 오세요 Come together please.
• 친구도 같이 오세요 Come here with your friend please.

누구 means who. There are a few ways to ask 'who?' in korean.
누구세요? Who is it (polite)
누구예요? Who is it (casually)
누구요?  Who is it (asking to repeat the name)
누구야?! Who is it (when angry)
누구습니까? Who is it (very formal)

happy studying ^_^

Learn how to read in Korean here.