like shopping, submitting a contact or other registration form, the way information is displayed on the page, galleries, calendar, event lists, registration of any kind, etc. They are all dynamic features that demand a little more complex coding. It is important for a designer to know what is expected, before the project starts. Integrating and adding these features will make a difference on the price you are paying, because some features are quite time consuming to put together. Even if you don't know what is a complex feature, look at other sites and ask the designer, tell them you like this or that on a website and they will explain to you the complexity.