The main risk is plugging a single-voltage device into a grid running at double its design voltage, which can destroy it instantly and sometimes dangerously. Countries run at either roughly 110-127 volts or 220-240 volts, and plug shapes differ on top of that, so travellers need to solve both compatibility and physical fit.
Here is the quick triage. Look at the fine print on each charger or power brick: anything marked 100-240V is safe worldwide and needs only a plug adapter. That covers virtually all phones, laptops, tablets, and camera gear made in recent years. The danger list is heat and motor devices, including hair dryers, straighteners, curling irons, kettles, and some shavers, which are often single-voltage. Running these through a cheap adapter, which changes only the plug shape and not the voltage, is how devices get fried.
For those items, either buy a proper voltage converter rated above the device's wattage, buy a dual-voltage travel version, or simply purchase one at your destination. Pack a universal adapter with USB ports, check your destination's plug type before flying, and skip the converter unless you truly need it.