CMS and ASP.net for web development

I'm new to web development. My understanding is CMS and asp.net are used for web development. To create web sites and to do 'asp.net programming with some of those web pages, do I need to use CMS or asp.net?. If we use the CMS cant we use the power of asp.net?. When to use asp.net and when to use CMS while creating web sites?