It's a question word used for yes or no questions, and it comes at the beginning of the question. A few examples: האם ירד אתמול גשם? - Did it rain yesterday? האם אתה יכול לעזור לי? - Can you help me? האם הם אוהבים לאכול גלידה? - Do they like eating ice cream? האם קר שם? - Is it cold over there? Do note however that it makes a question sound quite formal. In everyday language when asking a yes or no question, we simply omit the word האם.

האם = ה + אם The ה is not the article (ה הידיעה) but ה השאלה, that means that by definition it is a question. However, note that rhetoric question is formulated as a question, though it is a statement.

Yes. But אם - no