The Reading and Writing Sections of the General IELTS are completely different from the Academic IELTS. The General IELTS reading section has magazine, newspaper, and other types of articles and the Academic IELTS has school topics much like reading a text book. In the writing section General IELTS Task 1 is about writing a letter to a friend, boss, landlord and so on, but for the Academic IETLS Task 1 writing requires the analysis of a table, diagram or chart.
Of course, the biggest difference is perhaps the end goal. General IELTS is required for immigration and work. Differently, Academic IELTS is needed for university entrance or graduation.