What is the advantage of apache? How do you know if you should use it?

Question

Apache HTTP Server

Early to create microservice applications in different languages, frameworks. Periodically I saw images on dockerhub: php-apache-7.4 (and so on)
I don’t understand when it is needed (apache)?

The last time I ran a server on the Flask framework using Gunicorn. I correctly understood, it's like Apache? Or what's the point?

Answer 1

Summarizing comments.
Until you know why you need this or that technology, you should not screw it on.
To understand that you need it is extremely simple:
You look at the list of features, and if all your needs are satisfied by these features, and the existing solution does not satisfy everything, you can take it.
It's also worth looking at benchmarks that are close to your case if performance is important.
My opinion:
If you write a backend on flask, then it is a third-party web server, you only need to transfer the request from the domain to some internal server and add HTTPS + request caching and balancing.
In principle, any web server will cope with this task, and I would choose for simplicity and speed, for example Caddy