Macbook randomly shuts down/goes to sleep?

Why does my mac turn off/goes to sleep when I accidentally hit a random key on my keyboard? I'm not sure which key I'm hitting but everything closes then goes to sleep (e.g., I would have a notebook on my keyboard and when I take the notebook away, it would randomly hit a key or something + mac goes to sleep). I'm sorry if this is confusing I'm not exactly sure how to describe the situation.