Blast is designed to remove geometry that you select interactively in the viewport, as opposed to Delete which is a more procedural tool.
Subset of the input geometry to delete.
The type of the specified group. If this is not Guess from group, the group must be the indicated type.
Guess from group
Infer which type of group is specified based on the contents of the group.
Delete points affecting NURBS breakpoints in the specified breakpoint group.
Delete points used by the specified edge group.
Delete points in the specified point group.
Delete primitives in the specified primitive group.
The removal of geometry can change the effective normals on the surface. This option will recompute any point normals to ensure they reflect the result of the deletion.
Delete Non Selected
Negates the sense of the selection. Instead of deleting anything selected, will delete anything not selected. This is very useful to isolate some geometry.
Note that Breakpoints groups cannot be inverted with this toggle.
Fill Simple Holes
Caps complete holes that result from the deletion of points. A hole is said to be complete if it is a negative polygon i.e it has borders. This option works only with non-manifold geometry. After capping, it removes degenearate polygons that are formed during the deletion.
Fill simple holes is only enabled when point groups are used for deletion.
Delete Unused Groups
Remove any groups that are left empty after deleting points/primitives.