Usages of dum
Mia frato kuras en la parko, dum mia fratino legas libron en la hejmo.
My brother runs in the park, while my sister reads a book at home.
Mi lernas Esperanton dum mi trinkas varman teon.
I learn Esperanto while I drink hot tea.
En la kafejo mia amikino uzas la interreton, dum mi legas libron.
In the café my (female) friend uses the internet, while I read a book.
Elon.io is an online learning platform
We have an entire course teaching Esperanto grammar and vocabulary.