Open Collector, open what ??

[Adrian de los Santos]

Can someone explain me with apples and oranges, what its an open
collector connection, im trying to make a 5x7 led matrix, and in order
to turn on or off only some leds, everybody tells me that i need an
open collector.

But my understanding of electronics its very poor, i know how the logic
gates works and i have some simple basis on resistors and capacitors.

Open Collector its a new term for me, i have spent 2 days googling for
it and found some documents, but they dont even explain what a
collector its.

help please..

Thanks.