Both Wi-Fi and Bluetooth are under the category of wireless. SwitchBot Meters use Bluetooth, but a Wi-Fi option can be easily added.
The Meters use Bluetooth Low Energy (BLE) to communicate, so on their own, they are limited to Bluetooth range (e.g. around the house - like a Bluetooth speaker).
If you would like to monitor SwitchBot Meters remotely (e.g. away from the house), you need to use them in conjunction with a SwitchBot Hub (Plus), which relays the data of any in-range SwitchBot Meters to the internet using your local Wi-Fi network.
The reason the Meters use Bluetooth Low Energy (BLE) to communicate is that it's more cost-effective than Wi-Fi and it uses a great deal less power, so the batteries last a lot longer (in most cases 1 year) and the sample rate of the Meter can be a lot higher than if it used Wi-Fi. A lot of Meters with on-board Wi-Fi will sample once every 15 minutes instead of once every 2 minutes (like our SwitchBot Meters), and their batteries die after a couple of weeks instead of a year or more -- which is a real annoyance when you're measuring hard-to-reach places like a crawlspace under a house.
So with a SwitchBot Hub (Plus), you can not only add Wi-Fi capability but because of the lower-cost Meter, you can have a larger array of energy-efficient Meters pushing to the cloud for remote monitoring for a lot less cost. Plus, the SwitchBot cloud service is included in the purchase price, so there's no monthly fee for the Hub.
We may eventually move in the direction of Wi-Fi once it's possible to have more efficient systems.