Gauge Bean is a JavaBean which can display Gauge charts in the report.

A grid is a network of uniformly spaced parallel lines intersecting at right angles. The size of the grid rectangles can be defined under Properties in the File menu. If a grid is set, all objects are snapped to the grid, which means they are positioned so that their corners are located directly on an intersection of the grid. This allows for a more exact and uniformed layout for your report, however it is optional and can be turned off.

A group is any number of records considered an entity, grouped by some quality. Groups are for sorting and consolidating records with equal properties. Typically a group is composed of database fields with the same values.

An axis is a dimension in a chart used for putting values at their correct spots. The group axis is the dimension of the values by which the data values are grouped. For example, in a chart which maps salaries to employees, your group axis will be the dimension of the employees, since the employees are the values you are grouping the salaries by.

A group header is a rectangular area in your report labeled "Group Header". The group header is rendered once for every group in your report, at the top of the group.

A group footer is a rectangular area in your report labeled "Group Footer". The group footer is rendered once for every group in your report, at the bottom of the group.

A group name field is a field which returns the name of the current group. This name can be the string value of the field's group, however there is also the option to use a different value instead. The group name field is used to create the navigation tree for drilling down.

The group number is the number of the current group.
It can be added to the report as Special Field or it can be used as function in a formula.

A group selection is simply a selection by group, enabling you to select multiple values at the same time, the only condition for this selection is that they are all in the same group.

The group selection formula can be used to filter the groups that will be displayed in the report. It will be executed on the data fetched from the database but it can not be executed on the database, like it is possible with the Record Selection Formula.
It can be added to the report as Special Field or it can be used as function in a formula.