In English, you conjugate (change) the word "to be" according the subject. The following mean all "to be": I am you are he/she/it is we are you are they are There's a similar change in German, but there are more forms instead of am/is/are: ich bin du bist er/sie/es ist wir sind ihr seid sie sind The meaning is always the same, these are different forms of the verb "sein". Just as you don't say in English "you am" or "he are", you always use the appropriate form in German.

You are (Du bist), We are (Wir sind) ... There is no really different. It´s just that every person has an own word for "sein". That´s the hardest part to learn. For example: You are pretty. - Du bist hübsch. We are pretty. - Wir sind hübsch.