I like to know when I see the pci address like 00:1c.6 PCI bridge: Intel Corporation 6 Series/C200 Series Chipset Family PCI Express Root Port 7 (re

how to make sense of this address what is first 00 in 00:1c.6 and what is 1c in 00:1c.6 and what is 6 in 00:1c.6

Where is domain and is 6 is a bus? or slot? or function? I know there can be = number of bits than 1 byte to represent 15 pci devices connected to pci bus. But how many pci devices can I connect to single bus is there any limit? or its unlimited then it makes no sense. But I can relate to bus number, bus address, slot number but what the heck is pci domain. I couldnt find any source which explains specifically this, they talk about addresses and configuration space but skip the domain altogether.

How many pci domains are there are they predefined? And how to just read pci address string like 00:1c.6 in lspci output