What happens in a blast?

I'm curious, what exactly takes place during a blast? Is it an instantaneous event, or does it unfold over a period of time? Are there specific factors that contribute to its severity, such as the type of material involved or the proximity to nearby structures? Additionally, what kind of aftermath can one expect to see in the wake of a blast, and how does it impact the surrounding environment and people? Understanding the intricacies of a blast and its consequences is crucial for prevention, preparedness, and response efforts.