Selection tools in Silo.
Silo uses a component-based selection system.  Selecting objects in object mode allows you to edit their components in any other mode. Similar to layers, this allows you to work with only those objects of your scene which you select -- all others will be unselectable in the other modes until you select them in object mode.
There are five different selection modes: vertex, edge, face, object, and texture.  These are accessible from the right-click menu or from hotkeys "A", "S", "D", "F", and "G".  Performing a selection in any of these modes will allow you to edit that selection via the manipulator. (tutorial)
The selection system is customizable via Mouse Customization. (tutorial)  Open the Mouse Customization Dialog to view your setup.  Silo defaults to Select Visible functions, which only select the foremost layer of components, on left click, and Select Thru functions, which select all selectable components (including backfaces) under the cursor, on middle click.  Selection functions are conveniently grouped at the top of each drop-down menu.  You can Add, Subtract, Select New, and Select Complement.
You can also choose between Paint-Style Selection and Area-Style Selection, and choose to enable Persistent Selection.  If Selection > Area-Style Selection is checked in the menu, then clicking and dragging with a selection tool will draw a box, and the selection tool will be applied to everything within that box.  If Selection > Paint-Style Selection is checked, then clicking and dragging will apply to every component the cursor moves over, "painting" the selection like a brush.  To enable Persistent Selection, go to Options > General Options... and mark the Persistent Selection check box.  This will cause components to remain selected until they are explicitly deselected.
Enabling Soft Selection (Selection > Enable Soft Selection) allows the effects of editing your selection to be applied non-uniformly, with a falloff around the edges.  You will see a visual indication of the radius and falloff of the soft selection in the intensity of the vertex colors. The stronger the intensity, the more fully your edit will be applied. The falloff and radius can be adjusted using the Soft Selection Falloff Up/Down and Soft Selection Radius Up/Down commands, respectively.
Tweak is a time-saving selection tool, allowing you to quickly select and edit components of your model.  Try this: with nothing already selected, and the Translate manipulator active, Tweak select a component, drag to translate, and let go to deselect. The final deselect allows you to immediately tweak something else.  If something is already selected, Tweak will apply your edit to the current selection and will not deselect. Tweak can be used with any manipulator mode, and you can also perform regular operations, such as Extrude, on the temporary selection. Tweak defaults to Ctrl + left click, but can be re-assigned via mouse customization.