-Most guitars no matter if they are classical, electric or acoustic have 6 strings, although there are very exceptional cases of guitars with 7, 8 and 10 strings or with 12 strings that are known as double strings (they are played two at the time because they are very close, it's like playing a six string guitar). All guitars make the same notes so they are played in the same way although is not the same style of music or rhythm, but the notes are set in the same way.
-The clasical guitar also called Spanish guitar (because its origin is Spain) has three of the strings (the ones in the low that are the highest sounds) are made of nylon and the other three (the ones on top, the lowest sounds) are made of nylon fabric coated with steel spiral wire, the neck is wider than the other guitars and uses to have 19 frets. Also classical guitars have got a hollow body where the acoustic vibrations are created and that's why this guitar sounds.
-All the strings of the electric guitars are made of metal (steel, nickel or similar) the three on top are coated like the Spanish guitar but with metal not with nylon. The neck is narrower than the classical guitar and it's longer has got 22 or 24 frets (depending on the model). Most of the electric guitars don't have hollow body, their body is solid (without a hole) and they sound through an electric amplifier.
Some electric guitars are "semi acoustics guitars". They are used for Jazz and Blues, and although they are also plugged in an amplifier they have hollow body and they can sound a little bit even if they are not connected to the amplifier. (The solid body electric guitars also sound without amplifier but very little).
-The acoustic guitars have a hollow body (sometimes very big) similar to the classical guitar but the neck is much narrower like the one in the electric guitars and the strings are also made of metal (and not nylon) like the electric guitars but the strings for acoustic guitars have much more tension. Some acoustic guitars can be connected to an amplifier and some others not.
-Bass guitars are similar the electric guitars but much bigger and with only four strings, that are the same notes of the four strings of the guitar but an octave lower. Some bass guitars may have 5 or 6 strings.
In the other hand there are some groups especially Jazz bands that have a Double Bass and play most of the time with the fingers of the right hand (without the bow).
-In a band, the drums give the rythym to the singer and the electric, acoustic and bass guitars. Sometimes the classical guitar is in some ballads too, although is not very common in rock, heavy or metal songs.
There is a new didactic page in this site about tonality. In this website you can learn to tune all these instruments, to change their strings and put new ones, you can also read some useful and basic tips if you are going to buy a guitar or take better care of yours. You can also find information about the guitar classes that Miguel Angel González Aguado offers not only in the north of Madrid (Spain) but also guitar lessons online that you can take from any part of the World.