In which programming language do applets exactly fall ?

Question

As the sololearn app doesn't teach them in java.

Answer 1

The applets are applications in java for browsers, but i think they are not so interesting nowadays maybe is for that reason why sololearn doesn't teach them

Answer 2

Agree with @Jesus Gonzales:
Todays, with advent of Html5, Java applets for web pages are less benefit than security issues source ^^