  A plethora of two-dimensional (2D) materials entered the physics and
engineering scene in the last two decades. Their robust, membrane-like sheet
permit -- mostly require -- deposition, giving rise to solid-solid dry
interfaces whose bodily mobility, pinning, and general tribological properties
under shear stress are currently being understood and controlled,
experimentally and theoretically. In this Colloquium we use simulation case
studies of twisted graphene system as a prototype workhorse tool to demonstrate
and discuss the general picture of 2D material interface sliding. First, we
highlight the crucial mechanical difference, often overlooked, between small
and large incommensurabilities, corresponding e.g., to small and large twist
angles in graphene interfaces. In both cases, focusing on flat, structurally
lubric, "superlubric" geometries, we elucidate and review the generally
separate scaling with area of static friction in pinned states and of kinetic
friction during sliding, tangled as they are with the effects of velocity,
temperature, load, and defects. Including the role of island boundaries and of
elasticity, and corroborating when possible the existing case-by-case results
in literature beyond graphene, the overall picture proposed is meant for
general 2D material interfaces, that are of importance for the physics and
technology of existing and future bilayer and multilayer systems.
