What is PIC bootloader?

[F. N.]

PIC bootloader is a technology which can upgrade Flash programs all by the PIC processor itself.

It take advantage the self-Flash write/erase capability on PIC microcontroller and bring convenient to end user.

Depends on what communication technology is used, PIC bootloader can be classified as:
1. RS232C based serial bootloader
2. R485/J1708 based serial bootloader
3. CAN (controller area network) based serial bootloader
4. USB based bootloader
5. Ethernet based bootloader

The most frequently used bootloader are RS232 and CAN bootloaders.

[pascor]

Both serial and parallel ports on all new PCs are very quickly becoming obsolete. I strongly recommend using USB programmers instead of parallel or serial port versions since they are just as inexpensive and easy to use.

[F. N.]

That's correct. USB is available on many PIC chips, such as the popular PIC18F2550/4550, the new PIC18F14K50, etc.
On the other side, there are still many PIC chips doesn't have a USB function, which may still count on the UART port, CAN port to get new program loaded.

The other advantage we can take these days, is: the USB to Serial converter is getting cheaper these days, and all our bootloader has been widely tested with the popular USB to serial converters, such as FTDI, prolific PL2303, etc. We do carry one at our online store:
http://www.auelectronics.com/products/cables/cbl-usb-232.html