This article is from the Dissociation FAQ, by Discord (firstname.lastname@example.org) with numerous contributions by others.
Switching refers to a change in the configuration of who is "out",
"up front", or "in control" in a multiple system.
Switching may be as drastic as a complete switch between two alters,
where the new alter has no idea where sie is or how sie got there. It
may be as mild as a shift in the configuration, where one of the several
alters currently out departs and a new one emerges.
For some, switching involves little or no effort, nothing is lost during
the switching, and switching out of control does not necessarily mean the
alter doing so will lose anything either. For others, switching involves
anything from a brief fuzziness of recent memory or a small perceptual jump
to a complete sense of disorientation/fugue including time loss, not
knowing where one is, or what one was doing.