Audio: Difference between signal, channel, bus, track and strip

An audio signal is a representation of sound, typically using either a changing level of electrical voltage for analog signals or a series of binary numbers for digital signals.

It is a single audio pathway to transmit an audio signal. It may be a physical pathway or a digital pathway.
By definition, it only contains the audio signal of one audio source (for example a microphone).
It is important to understand that an audio channel is not the audio signal. An audio channel is the pathway used to transmit the audio signal. The audio channel contains the audio signal, but it is not the audio signal itself.
It can be think of the audio channel as a single lane road. The audio signal would be the cars driving on that road lane.

Audio tracks refer to recorded clips of audio that stand alone and can be played horizontally and simultaneously with each other.
In other words, audio track is an audio recording. When the audio signal of an audio channel is recorded, it creates an audio track.
An audio track can be the recording of one or multiple audio channels. When audio track contains only one audio channel it is called mono audio track, if the audio track contains 2 audio channels is called stereo audio track, if 3 channels called Lateral Surround, 4 channels called Quadraphonic, 5 channels Surround or Multichannel, over 8 channels there is Dolby Atmos, DTS:X...
An audio track may have been recorded in a physical medium or a digital medium.
When several audio tracks are combined in another audio track that would receive the name of audio Stems. So an audio Stem is an audio track of audio tracks.

It is a routing path that aggregates multiple audio channels or audio tracks. It may be a physical routing pathpathway or a digital routing pathpathway.
It is used to combine different audio channels or audio tracks according to the needs of the user.
The same as before, dependeing on the number of channels is called Mono Bus, Stereo Bus, etc.

It is not a concept related to the audio signal. It is a concept related to audio mixing and editing.
When mixing or editing audio, there are a some audio features that can be modified (compression, equalization, amplification, filters, effects, etc). The hardware or software used to modify those features usually has a series of controls (buttons, knobs, sliders, etc) that are grouped together visually.
That set of visually grouped controls that allow to modify the features of an audio fragment is called a strip.
So a strip is an editing and mixing concept and therefore it modifies the audio fragment to which it is associated: an audio track, an audio stem, an audio channel or even multiple of those audio elements at the same time. It depends on the user's configuration.