People normally do it to augment a meal or satisfy a psychological need. Negative images of snacking include potato chips, candy bars, ice cream and other usually high fat, non-nutritive foods. The truth is that there are many great snacks between the extremes of celery sticks and potato chips. The reason most people snack is the delay between lunch and dinner.
Most people eat lunch around noon.
Then, in another three hours or so, they are hungry again. If a snack is not consumed at this time, food will be over- consumed later, either as a late snack or overeating at dinner. So, a smart snack selection at this time will fill the hunger attack and prevent over-eating in the evening. Snacking also serves as a balm for moody moments. Bored or sad, a certain snack may be just right for that mood and fill the craving.