Modify panel > Make a vertex sub-object selection. > Modifier List > Object-Space Modifiers > Affect Region

Make a vertex sub-object selection. > Modifiers menu > Parametric Deformers > Affect Region

The Affect Region modifier is a surface modeling tool, primarily used with vertex sub-object selections while surface modeling. With Affect Region, transforming a selection of vertices can also transform vertices in the region that surrounds the selection. This can help you form a bubble or indentation in the surface of an object. The easiest way to see this modifier's effect is with a shallow, flat box object with plenty of subdivisions. The Affect Region modifier has a two-part, arrow-shaped gizmo plus numeric controls.

When you apply the Affect Region modifier, it assigns an arrow-like gizmo consisting of two points connected by a line. The base of the arrow is the start point. The length and direction of the arrow defines the amount of movement of the vertices. Any vertices within Falloff distance of the base of the arrow are translated in the direction of the arrow.

Because no points on the mesh are directly selected, this modifier doesn't depend on the topology of the input object. You can apply it to any renderable object. However, you can limit the effect by using a selection modifier like Mesh Select or Volume Select to pass a sub-object selection up the stack.

Note: The Affect Region modifier has traditionally been used primarily for fine-tuned modeling. However, for this application, you'll probably prefer the expanded capabilities of Soft Selection in Editable Mesh, Edit Mesh, Mesh Select, Volume Select, the HSDS modifier, and NURBS.