As Chris mentioned rake routes will tell you, but a quick explanation:
any product based routes will go to the products controller so:
GET /products # products controller index action
GET /products/:id # products controller show action
POST /products # products controller create action
PUT /products/:id # products controller update action
... etc etc
You'll also be given some extra routes however that go to a categories controller, this category will be a property of some product... so:
GET /products/:product_id/category # categories controller index action
POST /products/:product_id/category # categories controller create action
... etc etc
If you do something like:
match 'products/:id', :to => 'catalog#view'
you're overriding the default show
action of the route. Is this what you want? Likely not. Again, run rake routes
to find out what's going on.