A tantrum is an emotional outburst. They happen because someone is feeling a lot of emotions at the same time. A tantrum, meltdown, fit or hissy fit, temper tantrum, is usually associated with those in emotional distress, which is typically characterized by angerness, stubbornness, crying, screaming, violence, etc.
There are many signs that indicate someone is having a tantrum. The most prevalent sign is when pre-schoolers, school children throw temper tantrums because they want their own way. Other indications are throwing items or picking up items and throwing them away, aggression towards others, screaming, etc. They are easy to tell apart because these are all physical manifestations of an emotional outburst. When someone is having a tantrum, it is obvious that they are in distress and need support.
Tantrums happen for reasons ranging from developmental age to lack of sleep. All children go through different tantrum stages in their lives. They are common for preschoolers, school children, and even adults. When kids lack proper sleep it affects their behavior negatively. Lack of sleep can cause excess crankiness leading to a tantrum that is more severe than usual. Parents may find themselves dealing with children at the peak of their tantrum stages because that is when kids are learning how to use words and have better control over their emotions. As the child grows older the intensity of tantrums also decreases as they learn other ways to express themselves.