Twitter Users or Hashtags

I am new to Twitter though I apparently signed up for twitter as part of a class several years ago!  I am interested in following:

@NAEYC
@ZEROTOTHREE
@FredRogersCtr

I am new to using Twitter though I also must have signed up for it several years ago (probably for a class or school) and have been receiving post on my email for quite some time. I am interested in finding out more about Twitter and to see if it would be beneficial in teaching my Special Education classroom.