Audio / Video capture : a capture means the ability to take the video or audio output of a device (camera for instance) or applications (Logic for instance) and transform it into a usable source for other devices or applications - in our case, OBS.
DAW = Digital Audio Workstation : the software you use to make music, like Ableton Live, ProTools or Logic Pro.
FPS = Frames Per Second : for a video signal, it's the number of images per second. The standard is 30 FPS which is already higher than standard cinema (usually 24 FPS). These days, some HD TVs and streamers use 60 FPS which is especially important when you livestream fast action like video games.
OBS = Open Broadcast Software : a free open-source software that allows you to combine audio and video from various sources and send the resulting audio/video stream to Echio. It's like your own little TV production studio.