Knowing whether you have acid reflux, heartburn, or GERD is understandably confusing—the symptoms are often similar. The three conditions are actually all progressions of the same issue. Here’s what’s happening in your body to jump-start the process.

First, you eat something. It doesn’t have to be something particularly fatty, spicy, or decadent. The most common culprits, though, are acidic and fatty foods. Think citrus, chocolate, fried foods, tomatoes, and other things like that.

After chowing down, that food heads from your esophagus to your stomach, a space guarded by the lower esophageal sphincter. It’s a ring of muscle that closes up to keep everything in when food hits your belly. The problem comes in when that muscle doesn’t tighten or close up properly. Stomach acid can then leak back into your esophagus, causing acid reflux, heartburn, and GERD.

All three conditions are more common in people who eat too quickly, drink or smoke, are obese, have a lot of stress, slouch a lot, have Diabetes, or are pregnant. So how do you know which one you have? Let’s take a closer look.