It's a database primarily operated upon using a spreadsheet interface. You can create different representations (literally Views) of your data / rows. You can add custom logic "blocks" to rows / entries / tables that, for example, send a text message to a customer in the table.
You can arrive at Airtable as a product from first principles by basically just saying: most applications are CRUD apps atop a database with some custom callouts to external APIs. What if the database was super easy for a non-technical person to manage, we could provide data insertion / retrieval in a few standardized views, and there were integrations for the most popular 3rd party services upon record creation / editing / etc.?
You're not going to build a brand new consumer app on Airtable, but all of the backoffice and internal crap we write over and over and over again... it's a really good option for simplifying those processes and is accessible to non-developers.
Don't underestimate that.
All of this can be done ... without writing a single line of code, which is impressive!
What's old is new; what's new is old.