Strictly speaking a "DAC" is a "Digital to Analogue Converter" which is a specific and critical component of the audio processing chain that connects a digital audio processing system with your hearing.
However, it is also used to describe a hardware device that works as an "external audio device" specifically for replaying higher quality audio than can be replayed using the stock audio hardware on a computer.
I believe you are referring to the latter description when you are referring to DAC in this context.
A Sound Card is a peripheral device that can be inserted into a computer motherboard to add additional and possibly enhanced audio processing and interfacing capabilities. It differs from a "DAC" in that it will sit inside the case rather than outside the case (and connected via USB).
An AMP is short for "Amplifier". This component takes "line" level audio and amplifies it for use with speakers or headphones. These devices can be discrete devices in their own right, contained within speakers (Active Speakers) or contained within sound cards or DACs as discrete low-power devices specifically for driving low-power headphones or speakers.
Most "DAC's" will have an "AMP" as part of the device. This is less likely with a "Sound Card" as these will usually just drive other audio devices or headphones.
Most DAC's will operate using stock drivers either contained directly within the operating system, or using manufacturer provided drivers. Either way the driver will abstract the functionality of the hardware away from the software so you shouldn't notice a difference when using your sequencer application other than simply selecting the correct output device.