Secureboot uses the TPM (Trusted Platform Module) to store keys to signed bootloaders (the windows bootloader for example), and then tells the BIOS to not run unsigned bootloaders.
Dual booting is when you install multiple OSs on your system. the most common dual boot configuration is windows and linux. unless you run stock ubuntu, your Linux bootloader is not signed and will not function with secureboot enabled.
as seen in another post here its possible to hack the TPM requirement off, but for how long will this work? temporary fixes, especially security hacks, never last long and are patched quickly.
My recommendation to everyone who doesn't want to be locked out is Virtual machines. Virtualize your windows using QEMU/KVM. libvirt makes it really easy nowadays.
you have any idea how much of a massive pain in the ass that would be? not to mention it causes you to lose some functionality (ie: suspend to memory) Chloe pretty much explains it perfectly but ill add on to it that every time you update your linux system, the bootloader is overwritten. meaning the entire process of making it secure boot compatible has to be re-done