This article originally appeared in MindBodyGreen.

Chances are, at one point or another, you've had a gut feeling. Maybe someone instantly gave you a bad vibe, or you had a sudden and unexplainable urge to skip an event. But what are gut feelings, or "gut instincts," really? And should we always trust them? Here's what experts in science and spirituality have to say.

So, what exactly is a "gut feeling"?

Our gut feelings or instincts are similar to our intuition, though often a gut feeling will involve some sort of physical feeling as well—which isn't always the case with intuition.From a physiological perspective, neuroscientist and author of The Source Tara Swart, M.D., Ph.D., says, "Your gut feelings are a combination of your gut bacteria communicating directly to your brain via chemical messengers in the blood (cytokine transmission) and the gut neurons connection to the limbic (emotional and intuitive) part of the brain."And from a more spiritual view, clairvoyant intuitive and author of A Little Bit of Intuition Catharine Allan tells mbg that "people usually get an overall sensation of knowing" but how that knowing presents itself will be different for everyone, which brings us to our next point.