EdX is an online education provider that offers online courses, popularly known as “MOOCs” or Massive Open Online Courses, from top universities around the world. Currently, edX boasts a catalog of 1800 online courses created by these partner institutions.
EdX courses consists of pre-recorded video lectures that you can watch on a weekly schedule or when it's convenient for you. They also have readings, student discussion forums, homework/assignments, and online quizzes or exams. There is an example course titled DemoX, which is designed to show new students how to take a course on edx.org: https://www.edx.org/course/demox-edx-demox-1-0
Generally speaking, edX courses are free to audit (i.e. watch videos and complete assessments) but if you want to earn a course Certificate, you will need to pay. EdX is the only leading MOOC provider that is both non-profit and open-source.
EdX also offers a number of micro-credentials like MicroMasters, Xseries, Professional Certificate, and Professional Education. Here is a brief summary of each edX micro-credential:
The MicroMasters program grants credit that counts towards a Masters degree, if the learner who earned the credential is accepted into the on-campus program. MicroMasters contains a series of masters level courses.
XSeries was the first ever credential launched by edX, but it doesn’t seem to be something edX is investing in as much. The number of XSeries Certificate programs went down in 2017 from 45 to 32. XSeries consists of sequence of courses that help you gain a deep understanding of a particular subject.
Professional Certificates are similar to the MicroMasters and Xseries. As compared to MicroMasters, they do not offer a path to credit. As compared to Xseries, they are supposedly more employer friendly. Here is how edX describes them:
Professional Certificates develop the proficiency and expertise that employers are looking for with specialized training and professional education