Booting and BIOS basics

Yes. There is normally some sort of ROM (ROM, EPROM, FLASH) with startup code. Sometimes the ROM is in external chips, sometimes it is built into the processor itself. For embedded systems, the ROM usually holds all of the software.

As for how an embedded system boots, it depends on the system. There's no one standad like there is in the PC world. Embedded systems are custom made and vary widely. Some even use the same hardware as PCs, but most don't. For those that don't, you have to find out how the particular processor you are using starts up. Sometimes the processor manufacturer has sample boot code at their website.

You read the specs on the processor you're going to use. On reset, the processor jumps to a known address and you make sure you put code there. Typically called a reset vector.

If you have an OS you're using with it, that OS may take care of that part for you and put its own initialization there before jumping to your code.

You'll have to dig in if you're moving from a desktop to an embedded system.