While writing the code, we often need to print a particular object and see the result. In rails we use puts and p for that.
Both will display the result but there is a difference between them.puts prints the result by applying to_s on an object where as p prints the result by inspecting the object.

For example we have a class Product

class Product
  def inspect
    "Inside method inspect"
  end
end

 
Now we will create an object of Product class

puts Product.new
puts Product.new.to_s
p Product.new

Output will be:

#<Product:0x00000003461510>
#<Product:0x000000034614c0>
Inside method inspect
 

 Here puts will simply print the class object , but p does inspecting of the object, will give a string as output as the method name is inspected itself.
Another difference by example:

class Product
  def initialize(product_name, quantity)
    @product_name = product_name
    @quantity = quantity
  end
end
 
product = Product.new("Car",1)
 
puts product
puts product.inspect
p product

Output will be:

#<Product:0x0000000320bc98>
#<Product:0x0000000320bc98 @product_name="Car", @quantity=1>
#<Product:0x0000000320bc98 @product_name="Car", @quantity=1>

As you can see, puts prints the class name of the object along with the position of the object in memory. Whereas p on the other hand prints the class name and all the instance variables of the object. So if you put an object,  you need to add .inspect to the object.