How many strings does a standard guitar have?

Six, tuned E-A-D-G-B-E. The odd one out is the interval between the G and B strings, which is a third where all the others are fourths - an irregularity that makes chord shapes easier to grab with one hand and permanently annoys anyone trying to think about the fretboard logically.

The instrument's ancestors run back through the Spanish vihuela and the lute to the Arabic oud, which reached Europe through Moorish Spain. The modern classical guitar was largely fixed by Antonio de Torres in the 1850s, who enlarged the body and worked out the fan bracing that gave it enough volume to be a solo instrument in a concert room.

The electric guitar is a different idea rather than a louder version. It barely projects acoustically; the strings disturb a magnetic field around a pickup coil, generating a current that is a direct electrical copy of the string's motion. That signal can then be distorted, sustained and reshaped, so the amplifier stopped being reproduction equipment and became part of the instrument - which is essentially the sound of the second half of the twentieth century.