what are back links and what are account creation backlinks?

backlinks are  the main parts of SEO, and account creation backlinks are most usefull for site

here are some of theme.


 1: https://answers.microsoft.com
 2: https://medium.com/
 3: https://www.instructables.com/
 4: https://www.theverge.com/
 5: https://www.deviantart.com/
 6: https://www.intensedebate.com
 7; https://people.sap.com/
 9: https://www.minds.com/
 10: https://speakerdeck.com
11: https://www.ulule.com
12: https://www.viki.com/
 13: https://peatix.com/
14 : https://slides.com/