To answer your question, let me quote the website itself:
Manna is distributed by the People’s Currency Foundation as a basic human right that every person in the world is eligible to receive, for free...
The vision of Mannabase is to empower the people of the world by making cryptocurrency accessible and available to everyone, and to provide a tool for effective altruism to reduce poverty and inequality.
source: https://www.mannabase.com/about/
To answer your question, let me quote the website itself:
Thanks for the clarification, one more question is manna convertible and in which exchange houses can be sold?
You can only exchange Manna for btc at southexchange