Column groups and row groups

In tables and matrices, a column group or row group usually refers to a subset of columns or rows, respectively. Short names or notational names include col group or colgroup, and row group or rowgroup. They can have varying uses depending on context:

In mathematics, a partitioned matrix is an interpretation of a matrix as being broken down into submatrices which may be more precisely referred to as a collection of row groups and column groups
In web development, colgroup is a standard HTML attribute and an HTML event attribute, for example used for color formatting of entire columns in HTML tables. The colgroup tag acts as a "parent container of one or more elements". Rowgroup is another HTML attribute.
In reporting, colgroups and rowgroups can be used for constructing tables and matrices which dynamically adjusts the size of their columns and rows, respectively, by displaying the set of columns in the colgroup set.
In reporting, colgroups and rowgroups can also be used for grouping of collapsible categories in the presentation of a table. One example of a use case may be if a table contains a lot of detailed information, but there is a want to display summarizing information of groups in the same table.