Blender's Bevel tool is used to create chamfers or fillets from the edges of a mesh. You can either use it via the toolbar or by pressing the hotkey Ctrl B.

Loops are paths of connected edges, are one of the core concepts in 3D modeling. To select a loop, use the hotkey Alt LMB. If you're using the Emulate 3 Button Mouse option, double click on an edge instead. To add a new edge loop, use the Loop Cut tool, or hotkey Ctrl R and hover your mouse over an edge that runs perpendicular to the path you want the new loop to take.