Grove-T is a T-shaped hub. Is this remind you the HUB unit ? They are basically the same thing, just in different shape.This is also used for GROVE port expanding.
Notice: Grove-T is just a hardware expander, if you are looking for hardware and software(standard protocol) expander like I2C, Single-bus, please check PaHUB or PbHUB. If you connectted two I2C slave devices onto HUB that share the same adress, you will have problem getting I2C data from both.