title: Rails 4 relation tables
body: <p>Hello I am attempting to add categories to my posts and I am a little confused on how to set up the relation for this one.</p>
  
  <p>Should a post have_many categories or should a category have_many posts?</p>
  
  <p>Ideally what I want to do is have one table that I seed with particular categories which in my head is a table with id's and a simple alias column for each category name.</p>
  
  <p>When making a post I want a select with all the categories in place and just assign a value. So if I picked value = 1 it should probably place the "1" into the categories_id column which gets referenced and I know that 1 = Some category.</p>
  
  <p>Maybe?</p>