hey man, yeah its true there is a ton of stuff on that price chart the Maestro posted, its almost too much to explain, however the concepts arent hard to understand, they are just numerous. Best idea may be to search investopedia.com for key words he uses like "neck line," "chart pattern," "support line," or trend line,

in brief though, so that I may offer some resolution to your question, is that the neck line is the bottom trend line of the head and shoulders pattern, when price breaks it, it is considered a confirmation of the pattern and therefore a good predictor of future price action. Not all patterns are 100% but it seems to me that a head and shoulders pattern, when confirmed, is pretty legit.

let me know if this helps