It's a safe bet that most people's first introduction to CDISC is through the SDTM. This is a content standard that ensures clinical data is submitted in a consistent manner, helping reduce review time and facilitating cross study analysis. Another content standard, ADaM, aims to perform a similar function for analysis datasets. Likewise SEND defines standardized domains for non-clinical data.
Adoption of these standards is driven by regulators such as FDA and PMDA, who mandate that data must be submitted in these formats.
This post gives a very brief overview of each model, how they fit in with the wider clinical trial process, and how you can get maximum benefit from them.