Welcome to Steemit henri.bouhadana. Let me know if you got any questions about Steem/Steemit. The official FAQ can be found here and is quite extensive https://steemit.com/faq.html - Also, Steemit is just one of the sites using Steem the blockchain. We also have Dtube, Dsound and Steepshot if you prefer videos,music or pictures instead of blogging content. And many more of course!
thank you Janne ! will go through FAQ, tutorials, etc... you shared, I can see tons of infos around here !