Data Camp is a novel educational resource primarily established in order to provide a diverse range of Data Science education. With such diverse aim it inevitably provides excellent programming or mathematical/statistical resource as well. Courses about programming languages like R and Python include breadth of information levels, from initial learning of the language to specific applications in Statistics or Data Science. Users of this resource are not just assumed to be well educated in Mathematics to just dive in, range of courses are there to introduce students to a range of Mathematical and Statistical basics needed for Data Science applications as well as higher concepts like Machine Learning. As Danny Kaplan states in paraphrased quote from the Data Camp Blog - algorithms, statistical modeling, programming,... are all now fundamental base of modern work just a the Algebra and Trigonometry were not just that long ago in the pre-Data World. Hence, these courses are widely useful for the STEM field in general.
There are free and paid (at a very reasonable rate compared with general technical online learning staples like Lynda or ItPro) courses. Also, there is a "Community" section which consists of completely free materials produced by the site users themselves. Not any less useful, just the opposite. Typical courses, to quote Danny Kaplan yet again, are like what one expects from Hogwarts textbooks: they are multimedia resources. Structure of these courses is what I'd call retro-novel: modern education have drifted away from teaching students how to do things, not at the Data Camp. How-to is the core of the material but it doesn't end there. Practice problems are not "PISA-like" thrown at the student/user. There are typically hints and directions, helpful nudges toward the correct path. You learn on that journey. Something one could have received in Eastern European engineering classes of the yore - training aimed at developing capabilities, not just understanding. After you are done with a course you will be able to do something new.