How does a BluRay player work?

Blu-ray is the 3rd and probably last optical disc format used to distribute digital media. Assuming you do not have a engineering degree, it will take years of study and hard work to understand the details of it's operation. Read this for starts:

https://en.wikipedia.org/wiki/Optical_disc

A plastic disc is inserted in it. the disk is encoded with pits or photo-reactive dark spots made by a laser. The player grabs the disk with a hub clamp and spins it under a another laser that shines on the spots/pits and reflects back to a small mirror or detector. the reflection pattern is read by the player, and decoded into a sound and picture stream, that is passed on to the external television and or sound amplifier.

If you want a full technical description, this is not the place.

Wikipedia and other sources have good articles on the workings of many gadgets.

same as a DVD player.

like a regular dvd player

That's considerably shorter than the wavelength of invisible, infrared light that a CD player uses (780 nanometers), which is why DVDs can store more than CDs. A Blu-ray player uses an even more precise laser than a DVD player, with a beam of blue light shooting out of it instead of red or infared