Alert! Urgent Assistance required! Old user left baffled!

As the title says I'm feeling more than a little confused at some of the changes the site has undergone, I'm hoping someone would take a little bit of time out of their day and leave a comment below explaining to me what just is the resteem ability? I resteemed the following post: https://steemit.com/introduceyourself/@intelliguy/if-you-re-new-to-steem-or-steemit-and-you-aren-t-making-hundreds-of-dollars-yet-let-me-explain-why

I did this because it reminded me of my own experiences with the site when I first joined before I had to leave the site for the lengthy hiatus I've just shaken myself out of. However, I'm thoroughly confused as to what a resteem actually is and does, is it nothing more than a way of keeping an insightful piece up at the top of the page? I'm curious and ready to learn!