Here's a breakdown of how it works with ATAPI (Advanced Technology Attachment Packet Interface) drives, which are the standard interface for optical drives in most computers:

Data Preparation: The data you want to write is first organized and formatted by the burning software. This includes error correction codes and file system structures.

Laser Focusing: The optical drive contains a laser diode that emits a focused beam of light.  This laser is directed onto the surface of the disc.   

Disc Structure:  Optical discs have a layered structure.  The key layer is the recording layer, which is made of a material that can be altered by the laser.  Common materials include dyes (for CD-R and DVD-R) and phase-change alloys (for CD-RW, DVD-RW, and Blu-ray discs).   

Writing Process:

CD-R/DVD-R: For write-once discs, the laser heats the dye layer. The heat causes the dye to become opaque or change its reflectivity, creating "pits" (areas where the light is scattered) and "lands" (areas where the light is reflected). These pits and lands represent the binary data (0s and 1s).   
CD-RW/DVD-RW/Blu-ray: Rewritable discs use a phase-change alloy. The laser heats the alloy to different temperatures. A higher temperature melts the alloy into an amorphous (non-crystalline) state, while a lower temperature anneals it back to a crystalline state. These different phases have different reflectivity, allowing them to represent data.   
Reading Process:  During reading, the laser shines on the disc at a lower power.  The drive detects the differences in reflectivity between the pits and lands (or the different phases in rewritable discs) to reconstruct the stored data.   

ATAPI Interface: The ATAPI interface is the communication pathway between the computer's motherboard and the optical drive.  It sends commands to the drive (e.g., "write data," "read data," "eject disc") and receives data from the drive.  It's how the computer controls the drive's functions.   

Key Concepts:

Pits and Lands: The physical representations of data on the disc.   
Dye (CD-R/DVD-R): The material altered by the laser in write-once discs.   
Phase-Change Alloy (CD-RW/DVD-RW/Blu-ray): The material that can be reversibly altered in rewritable discs.   
Laser Power: The laser's power is precisely controlled during writing to achieve the desired effect on the recording layer.
Error Correction: Data is encoded with error correction information to ensure that even if some parts of the disc are damaged, the data can still be recovered.   
In summary, "burning" involves using a laser to create physical changes on the surface of an optical disc, representing data as pits and lands (or different phases in rewritable media). The ATAPI interface facilitates the communication and control of the optical drive by the computer.