What does it mean when someone says: 'you suck'.?
If 'you suck', it generally means you have no skill and/or talent or you are inferior. The use of thie word 'suck' in this way dates back to the 140s in the USA. Early Jazz musicians would say that a guy could really "Blow" if he had a good sound when playing the horn. If he couldn't play very well then they would say that he was "Sucking" on that horn. That's where the term "Suck" as being something bad came from.
e.g. 'He plays that horn so poorly that he must be sucking on it'
Hope this helps