Why play rules are not mentioned anywhere?

Question

Any game has some play rules and instructions but this app(sololearn) has no instructions and mentioned rules .. although it uses some! ..one can gradually discover them .. but why not shown publicly?

Answer 1

I believe it is bcoz of simplicity of game and players are developers .

Answer 2

I can guess but still don,t know what is the meaning of this message:
you are out of lives
and what would be consequences
I know that learning a section leads to 5 xp but i do not know the effect of referring to comments which are usefull for better learning in most cases..also about wrong answers..