RE: KEEP YOUR ACCOUNT SECURE! MUST READ FOR NEW USERS! @fredrikaa was hacked, but now has his account back!

Absolutely, it is a lot to wrap your head around when you are new, especially since there could be a lot of money involved.
There are many posts that go into detail about such things, a guy named @noisy has done a great service for us all and has gone in great depth in many of his posts to help explain such things.
Check out a few of his posts:

https://steemit.com/steemit/@noisy/we-just-hacked-11-accounts-on-steemit-1158-sbd-and-8250-steem-is-under-our-control-but-we-are-good-guys-so

https://steemit.com/security/@noisy/what-is-the-difference-between-a-password-and-a-private-key-s-on-steemit-how-to-make-your-account-more-secure-by-using-them

https://steemit.com/security/@noisy/public-and-private-keys-how-they-are-used-by-steem-making-all-of-these-possible-you-can-find-answer-here