On old computers (using BIOS) we had to create 2 partitions, one to mount / and second for swap.But on new systems with UEFI we need to create third partition EFI System in addition to those two partitions. What is the purpose of this partition?Update: does this partition is shared between a Linux distribution and Windows?
What is the purpose of UEFI partition?
boot;uefi
Via Wikipedia:ESP (EFI System Partition) contains the boot loader programs for all  installed operating systems (which are contained in other partitions  on the same or other storage device), device driver files for devices  present in a computer that are used by the firmware at boot time,  system utility programs that are intended to be run before an  operating system is booted, and data files such as error logs.Further, relating it to BIOS-mode booting:UEFI provides backward compatibility with legacy systems by reserving  the first block (sector) of the partition for compatibility code,  effectively creating a legacy boot sector. On legacy BIOS-based  systems, the first sector of a partition is loaded into memory and  execution is transferred to this code. UEFI firmwares do not execute  the code in the Master Boot Record (MBR), except when booting in  legacy BIOS mode through the Compatibility Support Module (CSM).