SO STOP FIGHTING ALREADY
Help out the new member!
There is light and lighting. First, you need to get the terminology down- it can be confusing and overlapping.
Obviously, you need LIGHT to make any kind of photographic image "Light- photos" is the name of the medium.
Available light simply means us the light that exists at the time and place you are shooting- some say "existing light". You are not adding or depending on artificial light such as s flash, tungsten, LEDor other traditional photographic light sources. It's it-is-what-it -s lighting. You may need to augment it, fill shadows, or leave it as is and apply various exposure and post-processing strategies.
There is LIGHT VOLUME- in layman's terms which can be LOW, adequate, or HIGH. In technical terms, light is measured by foot candles, lumens, etc.
In the olden old days of film photography low light was more problematic. Fast lenses, faster films, and push processing were some of the approaches. Oftentimes the results suffered from coarse grain, lack of shadow detail, insufficient depth of field or blur due to wide apertures, and slow shutter speeds. Nowadays, in digital imaging, we can employ higher IOS settings without too much excessive noise (grain), shoot with hand-held cameras at moderately high shutter speeds, stop down a bit more in low light, and employ high dynamic range settings in post-processing.
Shooting with regular equipment in total darkness is relegated to inferred and other special techniques.
"Natural Light" refers to various levels of daylight, weather conditions, and variation based on the time of day; bright sunlight, cloudy/bright, overcast, open shade, skylight, or sunlight entering through a skylight or window.
"Lighting" for me pertains to aesthetics of light- direction, harshness/softness.diffusion, and color temperature based on time of day or artificial light source.
Therefore
When you inquire about "low light" etc, what's your issue- exposure, depth of field, noise, contrast, ISO settings, artistic aspects such as moods, effects, etc?
Mention what you are shooting, what kind of gear you are using, and what result you are trying to achieve.
Obviously, for example, shooting sports action, portraits, landscapes, macro, birds, photojournalism, etc are each going to require different approaches and techniques.