If you are on Tumblr or any site that requires a login you have a username for it and a password. The problem with that is that if you have multiple sites you do business with you have multiple user names and passwords.
Remembering them all is a challenge. Some folks have a great memory while others have to write them down on a piece of paper. There are software programs that can help you manage all that information.
As security problems arise you have to put in new information to keep hackers and the bad guys of the Web at bay. Resetting passwords can be done easily on many sites, however there are times you have to call on the phone and have someone do it for you. We live in an age where information management is a must for every Internet user.
Make your usernames and passwords tricky, and hard for someone else to figure out. Be safe and most importantly give your info to no one if asked. Have fun on the web and be safe while doing so.