Here is the detail of what they are and what they are used for:

What are they?

They replace the standard red plastic reflectors (catareptidops) found in the lower corners of the C-HR's rear bumper, which have a very similar triangular/elongated shape. Unlike the originals, which are merely passive reflective plastic pieces, these are true active LED lights.

What are they for?

They have a dual function, aesthetic and safety. They are usually wired to operate in multifunctional mode (2-in-1 or 3-in-1):

Rear/running lights: These emit a solid red light (often with a "neon" or hazy effect) when you turn on your car's headlights.

Brake lights: When you press the brake pedal, the internal LEDs (the square-segmented ones you see in the photo) light up much brighter and more intensely to warn those behind you.

Direction indicators (arrows): Many models of this type also integrate orange/yellow LEDs with a dynamic/sequential effect (the light flows) when the arrow is activated.

In summary

They are mainly used to give a more modern and sporty look to the car ("tuning" style) and to improve the visibility of the vehicle at night or in foggy and rainy conditions, making the car much more visible to other drivers.