The product shown is a  Ciclux USB rechargeable bike tail light. It is designed to be waterproof and has multiple flashing modes for visibility and safety.
It is a USB rechargeable light, so no batteries are needed. 
The light is waterproof, making it suitable for use in the rain. 
It typically has multiple flashing modes, such as steady, slow flash, and strobe. 
Some models have a long-lasting battery, with a runtime of several hours. 
The light is easy to install on a bicycle.