Cloud technology is on a steady rise: in a survey conducted by the Institute for Data Communication (IDC), 60% of the respondents consider cloud computing as the most important technology when it comes to digitisation in companies. This means that it is ahead of Big Data and mobility. But what exactly is the cloud? How does storage of files and access management work in the large online cloud? Which problems can result and how are they resolved? This article will address these questions and explain the most important terms in cloud computing.