Vedas will translate to knowledge in Sanskrit. What makes this special is the fact that Vedas is considered to be the oldest text that you can find right now. A lot of people think that these texts are very philosophical.
Upanishads are considered to be a sub-category of Vedas that was not written at the same time that the original Vedas were created. There are still some people who question if the Vedas should actually be considered because this is considered to be newer as compared to the rest of Vedas. Take note that the inspiration of the Upanishads is still the text that can be found in the original Vedas.