A common concern people have is the outcome of eating food that is moldy. This happens when you are not paying attention to what you are eating and suddenly realize that you just ate half a sandwich made with bread that has some mold on it. Then you go “Oh, crap, I just ate some mold” and then you google it to find out if you are going to die ….
As with all things you eat, the first thing that must be said is this: If you are allergic to it, then you probably shouldn’t have eaten it. But, we’ll ignore that because if you are actually allergic to “mold” (or some subset of molds) than you already know what to do or not do.
Otherwise, the answer to the question is: There’s good news and bad news. First the good news. Mold is generally not bad for you (some molds are even good for you, or otherwise enhance food, as in those fancy smelly French cheeses). If you ate mold, just don’t worry. If you feel sick then maybe the mold is a problem, but most likely it isn’t.
Keep in mind, being less concerned with mold than one automatically might applies mainly to mold that was not sufficient in quantity or yuckiness to notice it BEFORE you took a bite, and even during the biting process. In other words, this does not necessarily apply to cases such as the above depicted bread.
The bad news is simple: If the food is moldy, then it may be old and otherwise contaminated with bacteria and stuff that is not good for you. If you are in a high risk group for such things, or pregnant and trying to avoid listeria, etc., then you might want to avoid old rotten food, and the mold itself, while not harmful, is a clue that the food is old.
As a general rule, soft food is more risky if it is moldy, while hard food (like hard cheese) can be cleaned up by scraping or slicing away the moldy part.
In my personal opinion, First Worlders are more worried about rotten food than they need to be, and throw away a lot of perfectly good food. Try to be less squeamish and check your priv before discarding things that scare you.
Some books related to mold and things moldy: