Todolist object in "Build a Todo List Application"

TodoList is written using capital letters and does not have any underscores - this means it refers to the model. So TodoList.count counts all the todo lists in the database. If something starts with lowercase letter and has underscores, it's a variable (local) or a method. If it also starts with an @ sign, it's an instance variable. This object was automatically created when Jason used scaffold - scaffold has a lot of magic in it, generates A LOT of stuff for you, and I agree, it can be confusing,because you don't see exactly what is going on under the hood. Generally this created the whole model, database migration and controller with basic methods inside, views etc. I personally don't think it's a very pedagogical approach (the scaffolds), so you'd need to read up on your own to see what this did exactly.