The purpose of a humidifier is to "moist" the air inside a home, which can become dry for a couple of reasons. On of them being having the heating on all day and, the other reason living in an arid climate. That said, having too much moisture in the air can have adverse effects like ruining your paint, create black mold and even damage the electronics in your home. 
You will know when there is too much moisture in the air when it feels muggy like in a steamy room after having a hot shower. If you want to remove moisture, you will need a dehumidifier. If you want to moisturize the air, you will need a humidifier such as the SwitchBot Humidifier.
Being an ultrasonic humidifier, the SwitchBot Humidifier does not heat up the water. Instead, it atomizes the water into a cloud-like mist by vibrating it via a small piezoelectric transducer and then, blowing the mist with a fan via a long spout neck that runs from the base of the 3.5 litre capacity water tank. The SwitchBot Humidifier disassembles into two parts - the water tank and the body, which integrates the fan and the electronic components such as the Bluetooth chip and the magnetic float water level sensor.
Some humidifiers use a capacitive sensor for detecting low levels of water, while the SwitchBot Humidifier uses a magnetic reed switch that is sealed off inside a short plastic stem. Around the stem, there is a magnetic ring, which travels up and down according to the water level. When the magnetic ring travels down, it energizes the magnetic reed switch, causing it to trigger a "low water level" alert.
The capacitive touch button led light cannot be disabled. After turning off the unit, the led light will be off but the fan will continue to run for up to 2 minutes. It is not specified why the fan runs after the humidifier is turned off but, it is most likely a safety feature designed to drain any left over voltage from the circuit since the SwitchBot Humidifier requires 24 volts to operate, which is a lot more than any consumer gadget.
The SwitchBot Humidifier is 30cm high with a 18cm diameter and 18cm depth; hence it's very compact and can fit on a bedside table. Operation is easy via a single capacitive touch button, which has an led ring around it to indicate the current speed of the fan (e.g. Speed 2/yellow, Speed 3/amber). The built-in fan is about the size of a laptop cooling fan and basically controls how much humidity is put out. The higher then fan speed, the more humidity the humidifier can put out up to 200mL (Milliliter) per hour.
Fan speed can also be controlled via the SwitchBot app. The app has a dedicated on-screen button with three speed settings, as well as a slider for sliding the fan humidity speed from 1% to 100%. There is also an automatic mode, which is designed to keep relative humidity level between 40% and 55%.There is also a small tray on the side of the humidifier body that contains an absorbent pad designed for essential oils. This, effectively, turns the SwitchBot Humidifier into an essential oil diffuser.

The reason why the SwitchBot Humidifier uses such high voltage is that it allows the humidifier to draw just 1 amp, which is about the same amp draw when charging a phone. This is much safer and makes total sense since the humidifier is designed to run for hours on end, which is safer using low amperage. The only drawback of using high voltage/ low amp, it's that it reduces the lifespan.
The SwitchBot Humidifier requires exactly 24V/1A to operate so, it will not work with a lower rated AC power adapter. If you won't be using the humidifier for long periods, it's a good idea unplugging it from the mains because even when the unit is powered off the bluetooth signal is still broadcasting.

The SwitchBot Humidifier has a plastic construction. The water tank is made of see-through plastic with a tinted finish, while the body is made of opaque plastic. The water tank sits securely onto the body. To remove it, you simply lift it off with the hands. 
The water tank has an inward lid at the top to prevent water from spilling out but, it also causes water to become trapped, making it a bit difficult when manually draining the water out of the tank. Even when tipping the tank upside down, getting the water out is a bit awkward. You can leave it to air dry naturally or you can use a tea towel cloth to pat dry the water tank, which also prevents water stains.
The SwitchBot app is useful, not only because it lets you control the humidifier but also because you can interface the Humidifier with other SwitchBot products such as the SwitchBot Meter, which is a hygrometer that reads temperature and relative humidity. 
There is also the SwitchBot Hub Plus or Hub Mini bridge cloud. A SwitchBot Hub is needed if you want to control the humidifier when you aren't home. The SwitchBot app requires connecting to a router or powerline adapter via 2.4Ghz connection. While the Humidifier connects to a router, it also needs bluetooth and location permissions to be enabled on your phone. You can buy the SwitchBot Humidifier from amazon.