Typically a millimetre or two over normal indoor distances, but the figure is conditional. Accuracy degrades on dark, glossy or steeply angled surfaces that return little signal, and over long outdoor shots in bright light. For critical work, take several readings and use a target plate on poor surfaces.

Almost always the target surface or ambient light. Quoted maximum range assumes a pale matt surface in reasonable conditions; a dark, shiny or angled target reflects far less back to the detector. Bright sunlight also swamps the returning spot. A target plate typically restores most of the lost range.

They tell the meter whether you are measuring from the front edge, the back edge, or a corner or tripod thread of the housing. Getting it wrong offsets every reading by the length of the instrument, which is a common and easily missed error - particularly when measuring from a wall into a corner.

Using Pythagoras to derive a dimension that cannot be measured directly - typically the height of a wall or the top of a structure - from two or three readings taken from one position. Its reliability depends on the instrument's inclinometer, so models without one give noticeably less trustworthy results.

Yes, but with reduced range in daylight because the returning laser spot competes with sunlight. A target plate helps considerably, and higher-specification models include a camera viewfinder that lets you aim precisely at long distance, which is otherwise the practical limit outdoors.

For most interior work, largely yes, and it is faster and needs one person rather than two. It does not replace a tape for measuring around curves or along a surface, for internal dimensions in tight spaces where the instrument will not fit, or where no return surface exists at the far end.

Measurements pass straight into a phone or tablet app, so dimensions land in a floor plan or quotation without being transcribed - which removes the transcription error that causes most measuring mistakes on site. Some apps also build a room sketch as readings are taken.