@gustavopeq said:
What's the difference between TV show on_the_air and airing_today?
Sorry, it might be a dumb question,
but I didn't actually understand the difference between the TV shows on_the_air and airing_today.
Can someone help me clarifying that?
Thank you!

I believe the explanation on each page is clear.

Airing Today
get https://api.themoviedb.org/3/tv/airing_today
Get a list of TV shows airing today.
https://developer.themoviedb.org/reference/tv-series-airing-today-list
That is, today. Just today.

On The Air
get https://api.themoviedb.org/3/tv/on_the_air
Get a list of TV shows that air in the next 7 days.
https://developer.themoviedb.org/reference/tv-series-on-the-air-list
That is, in the next 7 days.