Not knowing what Gore-Tex I thought it was a TeX variant for the vision impaired. According to Wikipedia: "Gore-Tex is a waterproof, breathable fabric membrane and registered trademark of W. L. Gore and Associates."
Yeah, it is a name for several types of fabric used in a lot of outdoor equipment. They all claim to be both waterproof and breathable, but in reality, they are mostly either one or the other. Waterproof Gore-Tex will fill with condensation, and breathable Gore-Tex will soak through. Pick your poison.
There are tradeoffs between waterproofing (hydrostatic head measured in mm) and breathability (measured in g/m^2/24h), but "one or the other" isn't really accurate, there are products that do very well at both.