Most people would look at their pcb which contains an 8051 and ask 'how do they get the program into it?'

They want to know what cables, hardware and software are needed.

You either have to remove the 8051 and put in an socket. (in a HVPP programmer)
Or you use an 'In System' method e.g. SPI, RS232, USB, JTAG ...

Every 'In System' method requires some sort of connection to a PC or external hardware. The RS232 or USB bootloaders probably have the necessary connectors cables already on the pcb. The SPI and JTAG methods need some sort of intelligent hardware or dongle.

Most people would regard the hardware that provides the SPI or JTAG interface as a 'programmer' whether intelligent or not.
The SPI unintelligent LPT dongles require a LPT socket on your PC.
The JTAG Wigglers unintelligent LPT dongles require a LPT socket on your PC.
The intelligent USB/RS232 devices tend to have better hardware interfaces and are more reliable than LPT dongles.

David.