what is /boot partition really for?

I'm reading a relatively old text on linux partions and file systems, it says:

Some versions of the Linux boot loaders cannot access a kernel that is outside the first 1024 cylinders on a disk. By putting the /boot partition at the beginning of the drive you can be assured of not having a problem when accessing the kernel at boot. This problem shows itself most often in cases of dual booting Linux along with another operating system that is on the first partition.

My question is: why a linux distribution may have "no access to the kernel outside the first 1024 cylinders" on a disk?

Also, what does "putting the /boot partition at the beginning of the drive" mean?

PS. The text is extracted from "LPIC 1 Certification Bible"