Electric guitars can be Solid Body, Hollow Body or Semi-Hollow Body. The main difference between these types are:
The size, weight and body profile of the guitar will be different and that will make a diffence in the way you approach and play the guitar. Just a quick pointer here:
As a general rule the solid body guitar is the most heavy and the hollow body guitar is the lightest. Obviously this is due to the amount of wood that is used in the construction of the body of the guitar.
Semi-acoustic guitars (referring to the semi-hollow and hollow body) are usually a bit larger than their counterpart, the solid body guitar.
Semi-acoustics are said to have a much more rich, deep and warm sound than the solid body guitar due to the increased mid-range that is captured. This gives the guitar a more acoustic sound.
In almost all cases a solid body guitar has a much longer sustainability than a semi-acoustic guitar. This is because the material of the body, i.e. the wood, helps the guitar sustain it's notes for longer. Therefore the more wood, the longer the sustainability.
Semi-acoustic guitars generally have a problem with feedback. A semi-hollow body guitar has a wooden block running down the centre of the guitar, which helps reduce feedback problems. The block also slightly strengthens the body of the guitar.