Which partition should be bootable, and why?

Using Debian 12.5 Bookworm, 64bit I wanted to teach myself how to partition my disks for my needs, so I did this: ——————————————————————————————| [!!] Partition Disks |—————————————————————————————— This is an overview of your currently configured partitions and mount points. Select a partition to modify its settings (file system, mount point, etc.), a free space to create partitions, or a device to initialize its partition table. Guided Partitioning Configure software RAID Configure the Logical Volume Manager Configure encrypted volumes Configure iSCSI volumes LVM VG deblvm-vg-home, LV deblvm-lv-home - 14.7 GB Linux device-mapper (linear) #1 14.7 GB f ext4 /home LVM VG deblvm-vg-usr, LV deblvm-lv-usr - 14.9 GB Linux device-mapper (linear) #1 14.9 GB f ext4 /usr LVM VG deblvm-vg-var, LV deblvm-lv-var - 14.9 GB Linux device-mapper (linear) 1# 14.9 GB f ext4 /var Virtual disk 1 (vda) - 107.4 GB Virtio Block Device 1# primary 1.1 GB B F ext2 /boot 2# primary 53.2 GB F ext4 / 5# logical 8.6 GB F swap 6# logical 14.7 GB K lvm 7# logical 14.9 GB K lvm 8# logical 14.9 GB K lvm In some places I saw that I need to make at least one partition bootable to make the system work. that's what I've learned: * If you use BIOS, then you need to flag /boot as bootable. * If you use UEFI, then you need to flag / as bootable, or /boot/efi. * You must install grub to the bootable partition (e.g. vda1 and not just vda) So my questions are: Is this correct? Am I doing things wrong? Where can I learn about which partition should be bootable and which shouldn't, and why? Thank you