"DAC" stands for "digital-to-analog-converter." It's the device that receives a digital file (FLAC, ALAC, MP3, AAC, OGG, etc) and converts the 1's and 0's to an analog waveform that can be used to make a transducer (speakers or headphones) move in and out and produce sound....
Amp is short for "amplifier". It amplifies the analog waveform created by the DAC and provides the power to drive your speakers or headphones.
These are 300-ohm...