Android boot architecture compared to desktop boot process After reading this answer and pointing article: Can somebody explain the boot process of an Android device?

My Samsung S3 have CyanogenMod installed. There is probability while installing custom recovery via Odin to brick your phone.

How does boot process relate to installing custom recovery? Is custom recovery stored in device's BIOS (CPU ASIC??)? 

I'm looking for information, about how bricking works (in analogy to PC).
On PC you "brick" computer when your BIOS flash fails rest is handled by bootloader. It could be recovered by dismounting and reflashing bios chip.

So I assume Android devices must have some kind of BIOS also and switch at some point to start booting from media. Is it correct?

On PC if you do not have any OS or it is corrupted you can use different media (floppy, CD) to boot.
Why is it not possible (from what I know) to do such a boot from Memory card?

By my undersanding, as long as BIOS is not corrupted it should be of no problem to boot/reinstall system?

Person installing my recovery told me to ONLY clear cache folders while chaning OS using recovery. So that would mean I cannot touch any core OS functions? Why is that. On normal PC I could just insert CD with new software and install OS from scratch.

The only explanation comes to my head is that BIOS and System is same thing?
To put it simply, it is not designed for users to "boot from Memory card" as you put it.  It is an embedded device and is designed as such.  Android devices are typically not meant for the end user to install software via external media.  They are specifically designed for additional software (not new OSes) to be loaded via some network connection.  The initial boot parameters are really going to be dependent on the product.