control is the device Address which you will determine by reading the DATASHEET for that device...

Example 1... for a DS1307 RTC chip, this Address is $D0.
Example 2... for a 24LC64 EEPROM, this address is in the range $A0-$AE.
Example 3... for an MCP23008 I/O Port Expander, the Address is $40-$4E.

It means you can have multiple devices co-existing on the same bus, as each will have their own unique device address, and will only respond to their own control byte.

Label is as you've already determined, the Label which the program will jump to if there is an error... in this case the I2C slave device fails to respond with an acknowledge. (it is actually in the manual). You can make use of this feature to easily detect if an optional device has been installed.