Gain refers to the increase of a signal's strength between an input and output port in a signal's path, such as an amplifier, audio mixer, or powered speaker and is measured by the signal decibel's increase (e.g. +4.02dB). In the past, pushing the gain past a signal's limit would often change a sound's timbre, with the most notable example being distortion, like on an electric guitar.
Volume refers to the perceived loudness of an audio signal, and is often measured simply (like on a TV or car radio) instead of with actual measurements, like decibels, which technically measure the pressure level of a sound wave. Adjusting the volume won't change the timbre of a sound.
In the context of an audio mixer, like the RODECaster Pro II, there is the microphone signal, which is usually low. Inside each channel's settings is an option to raise its input gain, which brings up the relatively weak microphone signal strength up to an audible range. When setting a channel's volume with a fader, what you're actually adjusting is that channel's maximum volume.
Put simply, gain refers to the change in signal strength that occurs between a signal component, wheras volume refers to the max level of loudness of an audio signal.
Imagine a complex sound, like a metal cabinet falling over. Parts of the sound, like the metal clanging, produce a higher pitch, while other parts, like the thud of the cabinet's mass hitting the ground, produce lower pitches. Frequency Response refers to the frequency makeup of the sound in its totality.
Audio-Visual (AV) - a term that referring to any media that feature both a sound and visual component.
Chroma key - a visual-effects technique most commonly associated with green screens where a color hue gets selected to remove background of a video clip/image or layer it onto a new one.
Clipping - A form of audio distortion that occurs when a channel or track is pushed to an output voltage beyond its maximum capacity, resulting in the audio wave's peaks being flattened.
Compression - Dynamic Range Compression is an audio effect that reduces the volume of loud sounds and increases the volume of the quiet sounds in an audio source, thus compressing the audio's dynamic range.
Decibel (dB) - a unit of measurement that expresses two values logarithmically. Since humans perceive sound pressure logarithmically, it works well as a measurement for perceived loudness with the base value being the threshold of perceptible sound.
Digital Audio Workstation - Computer software that allows for the recording, editing, and processing of audio. DAWs include Audacity, Reaper, FL Studio, Ableton Live, and Logic Pro.
Equalization (EQ) - the process of boosting and attenuating certain frequency bands of an audio signal
Faders - sliders on an audio mixer that adjust a parameter, typically, channel volume.
Frequency Response - the quantitative measure of magnitude for various frequency bands, (e.g "high/low end" and mid frequencies) of an audio signal.
Gain - the measure (typically in +dB) of a signal strength increase between an input port and an output port.
Noise Floor - the level of noise that is present in an electrical circuit or component. This noise can take the form of a hum, hiss, rumble, or other low-level sounds.
Phantom Power - Equally balanced power sent through the balanced signal wires inside of audio cables to power condenser microphones
Post-Production - The stage of audio production that occurs after recording. "Post" refers to editing, rearranging, and processing the recorded audio.
Proximity Effect - The increase in bass frequencies that occurs when an audio source is close to a directional microphone.
Track - a single layer of audio that exists within a larger recording.
XLR Cable - a cable with cylindrical, 3-pin connectors that are used primarily for sending balanced audio signals, but can also be used for sending video signal and professional lighting control.