A lap steel guitar is one type of steel guitar, from which other types developed. There are 3 main types of lap steel guitar:
Lap slide and resonator guitars may also be fitted with pickups, but do not depend on electrical amplification to produce their sound.
The common characteristic is that the strings are elevated above the fretboard, typically to about half an inch, and rather than being pressed to the fretboard, are fretted with a steel (steel bar) with the left hand, moving it up and down the strings to create a sliding sound while the right hand plucks the strings.
Guitars designed exclusively for lap playing typically have modified necks that make conventional playing impossible. The hollow neck acoustic lap steel guitar popularised by Weissenborn extends the body cavity behind the neck all the way to the head. The square-necked resonator guitar has a strengthened square profile neck allowing heavier gauge strings and/or higher tunings than a conventional guitar. The electric lap steel guitar typically incorporates the entire neck into the solid body of the guitar, again providing extra strength.
A lap steel is designed to lie flat on the lap while playing, and hence can have almost any shape, from a simple square plank to a guitar-like shape. If standing, a lap steel guitar can be worn hanging on long straps in front of the belly, or it can be mounted on a stand.