We report on an exploratory study, which aims at understanding how development tutorials are structured, what types of tutorials exist, and how official tutorials differ from tutorials written by development communities. We analyzed over 1.200 tutorials for mobile application development provided by six different sources for the three major platforms: Android, Apple iOS, and Windows Phone. We found that a typical tutorial contains around 2700 words distributed over 4 pages and including a list of instructions with 18 items. Overall, 70% of the tutorials contain source code examples and a similar fraction contain images. On average, one tutorial has 6 images. When analyzing the images, we found that the studied iOS community posted the largest number of images, 14 images per tutorial, on average, from which 74% are plain images, i.e., mainly screenshots without stencils, diagrams, or highlights. In contrast, 36% of the images included in the official tutorials by Apple were diagrams or images with stencils. Community sites seem to follow a similar structure to the official sites but include items and images which are rather underrepresented in the official tutorials. From the analysis of the tutorials content by means of natural language processing combined with manual content analysis, we derived four categories for mobile development tutorials: infrastructure and design, application and services, distribution and maintenance, and development platform. Our categorization can help tutorial writers to better organize and evaluate the content of their tutorials and identify missing tutorials.