i read it, and i'm not certain what they're talking about either, but i think the first person was trying to explain something and did it incorrectly or fed incorrect information. i've never studied 'sorcery' but i'm pretty sure it's the same as witchcraft, just another name [like a male witch calling himself a warlock or wizard] sorcery does sound darker, so in a way, someone who focuses on negative spells such as curses, might call what they do 'sorcery' instead of 'witchcraft'. these are just my speculations as i've never come across a difference beyond what terms people are comfortable labeling their craft with.
We use our minds eye as our wand etc. In which requires a lot of visualization, concentration and willpower without any aid from tools. Which means that a sorcerer can cast any means of magick anywhere unnoticed, which comes in real handy at times. Oh and by the way a sorcerer cast white, grey or black magick not just black.