Formal and informal greetings

When we first meet someone, or we found someone we allready know in the street, we use the greetings to start a conversation or to introduce ourselves. But there are different types of greetings depending of the situation we need to use them.

There are formal and informal greetings. We use formal greetings when we meet an important person and we use informal meetings when we meet someone we allready know or when we meet someone familiar. 

Here's a video where we can learn some formal and informal greetings and when we can use them.