EFI System Partition

The EFI system partition (ESP) is Article description::a formatted partition containing the primary   or kernel image(s) for installed operating systems.

Kernel
Advanced partition selection ( CONFIG_PARTITION_ADVANCED ) and EFI GUID Partition support ( CONFIG_EFI_PARTITION ) must be enabled:

ISO8859-1 codepage must be enabled too, in order to mount the EFI partition:

Characteristics
For creation instructions see.

will show it with the boot, esp flags:

will show it with partition code EF00:

Its filesystem can be created :

Size considerations
100 MiB should be enough for some primary bootloader payloads such as kernels or boot loaders such as  2 or Windows. This forums post however suggests giving it more space if a distribution kernel is used.

Mount point
An entry in is not needed for booting but might be useful for  manually.

Standard layout
There is a standard layout for the ESP. Vendors and distributions are supposed to put their stuff into vendor specific directories.

Here the Microsoft subtree - and also the Boot subtree - was created by an earlier installation of Windows 10 Creators Update. The Boot subtree is the fallback directory. If UEFI can't find any vendor specific directories it will boot from here. In a multiboot environment with properly set up vendor specific subtrees the Boot subtree can be deleted.

UEFI boot items
Computers with UEFI usually provide a boot menu and a configuration tool for creating, sorting or deleting boot items. The content of the ESP is visible to these tools and creating a boot item is like choosing the medium from a given selection, then surfing through the ESP and selecting the item, e.g bzImage-4.9.76-r1-gentoo.efi.

Alternatively, can be used for generating the UEFI boot items.