The “kernel” is the core of the operating system. Modern processors run in two different modes, kernel mode and user mode. When in kernel mode, they do things like handle task switching and task time allocation, manage virtual memory, basically all of the internal operating system type stuff. User mode is generally used for running tasks, whether the task has admin privileges or not. Device drivers run mostly in kernel mode.
When a task royally screws up, the OS will usually just kill the task, no harm done. When something screws up in kernel mode, this often results in a kernel panic. This just means that there has been a fatal, unrecoverable error in kernel mode.
“Kernel panic” is a unix term, and is used by Macs since their OS is unix-based. Windows has kernel panics as well, but Microsoft calls them “stop errors” (and everyone else just calls it the Blue Screen Of Death).
A Windows kernel panic can be caused by hardware problems, but more often it is caused by a misbehaving device driver. This is due in a large part to Windows machines not having any form of central control. Anyone can make hardware and software (and their associated device drivers) for Windows. Macs are much more controlled, with only a few supported hardware platforms and all software controlled by Apple. This makes device driver type errors much more rare on a Mac. Most Mac kernel panics therefore result from bad hardware.
You could have a failing disk, as beowulff suggested. If you are handy with hardware, you might try removing the Mac’s CPU and memory and reinstalling them. Sometimes things shake loose causing hardware errors during runtime. You could also have a failing system board, CPU, or RAM. Corrupted system files on the disk can also cause kernel panics. You can try a system repair, though if the corrupted files are the result of a failing disk, this may only provide a temporary fix at best.
Apple has some troubleshooting guides related to kernel panics on their web site. You may want to start there.
Macs can get viruses and malware, but that sort of thing is pretty rare. It’s much more likely that you’ve just got some sort of hardware issue going on. I wouldn’t worry too much about corrupting something on your MacBook. I would however worry that your files may not arrive fully intact on your MacBook. Whatever is causing the kernel panic could also cause your files to get corrupted.