guys

In English, there's not a really good word for addressing a group of people. If you're talking to one person you say "you":

How are you?

But there's some disagreement about what to say to a group of people. English speakers use different expressions depending on the region and dialect, but one common expression is "guys". For example, at a restaurant with a large group of friends you can say:

Hey guys, are you ready to order?

"Guys" technically means a group of men, but it's usually OK to use it for mixed groups of men and women, or even for groups of all women.

In very formal situations, avoid calling a group of people "guys". Instead, use a phrase like "everyone":

Everyone, thank you for coming.

I have to talk to you.

You usually use this phrase when you're just about to give someone bad news. It's often used when you are breaking up with a boyfriend or girlfriend, when telling your boss that you're quitting your job, and so in.

If you say "I have to talk to you" to someone, the most likely response will be "What's wrong?"