A tantrum is a result of not getting their own way, frustration, wanting something and not getting it, sometimes it's because they haven't got the language or understanding yet (like toddlers).
A meltdown can look very similar to a tantrum, but it's not about trying to get their own way or they are annoyed/upset because they can't have something..
a meltdown with someone with pda can happen if the child is being asked to do something they simply cannot cope with. So it can look like the child is simply being difficult or not doing as they are told/or having a tantrum because they are being asked to do something they don't want.
A meltdown is caused by fear/anxiety/frustration/sensory issues/masking. There's no reasoning with the child. Logically they are gone, their entire senses are utterly overwhelmed. It's not something you can talk through, or they are doing willfully or purposely..they have no control. It's also very frightening for the child, almost like a panic attack, a rush of adrenaline and cortisole. Most don't fully remember why or what happened to cause it, not remember what happened during it. Where a tantrum, they are more in control, and deliberately say or do things to cause hurt to people or objects. During a meltdown they are more likely to injure themselves and take a long time to recover because they are exhausted.
Tantrums should be ignored so as to not reward the behavior, privileges/treats removed, as it is deliberately behaving in a naughty or wilful bad behavior.
Meltdowns are not bad behavior and shouldn't be punished. The child needs need to be kept safe and helped to recover. They peak and eventually the body slows down and the child calms down. The child needs to be soothed, made to feel safe and secure.
There is a difference