The annotation of textual information is a fundamental activity in Linguistics and Computational Linguistics. This article presents various observations on annotations. It approaches the topic from several angles, including Hypertext, Computational Linguistics and Language Technology, Artificial Intelligence and Open Science. Annotations can be examined along different dimensions. In terms of complexity, they can range from trivial to highly sophisticated, in terms of maturity from experimental to standardised. Annotations can be annotated themselves using more abstract annotations. Primary research data such as, e.g., text documents can be annotated on different layers concurrently, which are independent but can be exploited using multi-layer querying. Standards guarantee the interoperability and reusability of data sets. The chapter concludes with four final observations, formulated as research questions or rather provocative remarks on the current state of annotation research.