7, 8, and 9 string electric guitars are types of electric guitars that have extra strings beyond the standard 6 strings. These guitars are typically used by guitarists who want to expand their range and explore new possibilities in their playing.

7 string electric guitars have an additional low B string, which extends the range of the guitar down to a lower pitch. This allows for more complex chord voicings and the ability to play lower notes more easily.

8 string electric guitars have an additional low B and low F# string. The extra strings allow for even more extended range and more possibilities for chord voicings and note choices.

9 string electric guitars have an additional low B, low F#, and low D string. The extended range of these guitars can be used to play low notes that are not possible on a standard 6-string guitar.

Some popular brands that make 7, 8 and 9 string electric guitars include Ibanez, ESP, Schecter, and Jackson. These guitars are mostly used in Metal and Progressive Metal music, but also can be used in other genres as well.