Blockchain technology has gained tremendous popularity both in practice and academia. The goal of this article is to develop a coherent overview of the state of the art in blockchain technology, using a systematic (i.e., protocol-based, replicable), multivocal (i.e., featuring both white and grey literature alike) literature review to (1) define blockchain technology, (2) elaborate on its architecture options and (3) tradeoffs, as well as to understand (4) the current applications and challenges, as evident from the state of the art. We derive a systematic definition of blockchain technology, based on a formal concept analysis. Further, we flesh out an overview of blockchain technology elaborated by means of Grounded-Theory.