what is an "Adressable" I2c device, and what does it mean?
Unlike most i2c devices, this one has no user adjustable address pins. The 3 address bits are set internally at the factory. You must buy different part numbers so you can put more than one on a single i2c bus.

What it means by addressable is that i2c requires a unique device address for communication on the bus. It's part of its protocol. Since this device only has 3 bits of addressing, only 8 unique addresses can be on a bus. You could use more by having multiple buses or a bus switch or multiplexer.

Or just get a device with multiple adc inputs.