Why a laptop and not a hair dryer?

A laptop doesn't purposely generate heat.

A hair dryer does and at a temperature close to boiling point.

As a quick example, It takes more energy (heat) to boil a litre of water (just getting it to boil and not keeping it there) than it would be to charge about a 100 standard laptops.

The average converter can only convert about 4 laptops worth of power.

Actually most all laptops don't need a converter, they just need a plug adaptor, something you can get anyplace for a few dollars. Read the specs on the laptop. If it says something like "100-240 VAC 50/60Hz" then it will work anywhere in the world. Perhaps someone miss-informed you.

A hair dryer uses a lot more power, and any converter would need to be big and heavy. It's actually cheaper (and much less to carry around) to buy a new hair dryer that is rated for "dual voltage", i.e. it has a 120/240 volt switch on it. Then you just need a plug adaptor,

A plug adaptor is just a little passive thing that adapts the use plug to a plug for the other country, different size and spacing. That's all.

A laptop power supply supplies a voltage DC that simply charges its internal battery. It can be left attached when using, but does not have to be. Most such power supplies will accept 110 to 250V. AC operation. It is unlikely that if it has a grounding pin, it is actually connected (no wire for it in the mains cable), as these devices are usually "double insulated" ( a square symbol with another square inside it, look on the case). No earthing is necessary.

A hair drier works on AC mains voltages. They also commonly are "double insulated", and cannot be earthed.

Bill Russel has given you good advice.

The "facts" you need about electricity are printed on every device.

You should understand the meaning of : Volts, Amps, and Watts.

Your hairdryer might use 1000 Watts (a lot of power to generate heat).

An LED night light might use 1 Watt (a small amount for cool light).

The importance of understanding Watts is choosing extension cords, adapters, outlets, and power supplies. Extension cords and converters also have ratings for the number of Watts they can carry.

Overloading them can damage equipment and/or start fires.

The reason any electrical device uses more Volt-Amps or Watts than another electrical device is because it has less input impedance than the other device and thus draws more input current when both devices have the same input Voltage. A particular hair drier that uses more Watts than a particular laptop has a lower input resistance than the laptop. However if a particular hair drier has a higher input resistance than a particular lap top then that lap top will use more power than that hair drier. But hair driers customarily offer a less input resistance to the ac source Voltage that furnishes it`s power than do lap tops. Consequently hair driers customarily use more Watts than lap tops. Both devices usually have the input Volt-Amps or Input Watts listed on their name plate.