In this paper a general presentation of Corpus Linguistics is provided by explaining what a linguistic corpus is, how it is related to other types of data, why it is necessary to annotate it, and what the annotation process is like. Some of the more common tasks in corpus-based linguistic research are also reviewed, such as obtaining frequency lists, exploring concordances, or finding co-occurrences (collocations) and other types of contextual information. Throughout the text, an attempt is made to show the relevance of this type of data for linguistic theory, in particular for use-based models, such as the cognitive and functional ones.