The edX platform consists of two primary user interfaces: the LMS and Studio. The LMS is what students use to interact with the course material, the instructor and each other. It is the part of the edX platform that most people are familiar with. Studio, on the other hand, is the underlying foundation of your course--it is the tool used by instructors to build and publish a course to the LMS.
Using Studio, you will be able to create an outline of your course by creating a simple hierarchy of modules, lessons, concepts, etc. Once created, the elements are easy to rearrange...you simply just drag and drop them. With Studio you can design your course from start to end and then publish to your students or you can create it one week at a time as you go.
Studio lets you build your course content in a way that intermixes content of various types: short videos, exercises, readings, tests and more to create learning pathways for your students. Adding new teaching elements is as simple as drag and drop. Studio comes with a broad suite of content types for videos, documents, interactive quizzes, etc. but if you don't find the exact tools for your course, the platform is extendable because of its XBlock architecture.
Studio allows you to collaborate with course co-authors as a team to build the course. The short 8 minute video above gives you an overview of the power and flexibility of Studio.