Live View
A mode that shows a continuous sensor feed on the rear screen instead of, or as well as, the viewfinder.
In depth
On a DSLR, live view raises the mirror and switches to contrast or on-sensor phase detection, which is slower but far more accurate than the dedicated autofocus module — there is no calibration error because focus is measured at the imaging plane itself. It also allows magnified manual focusing, which is why tripod and macro work almost always uses it.
Examples in practice
Focusing a macro shot at 10× live-view magnification places the plane exactly on an insect's eye rather than its wing.