What is a Balalaika

The balalaika is a family of Russian stringed instruments with a characteristic triangular body and three strings.

It includes instruments of various sizes, from the highest-pitched to the lowest: the piccolo, prima, secunda, alto, bass, and contrabass balalaikas. The prima balalaika is the most common. All have three-sided bodies; spruce, evergreen, or fir tops; and backs made of three to nine wooden sections (usually maple) though the Russian built one I repaired had a plastic body.

The prima balalaika, secunda and alto are played either with the fingers or pick, depending on the music being played, and the bass and contrabass (equipped with extension legs that rest on the floor) are played with leather plectra. The rare piccolo instrument is usually played with a pick.   

The most common solo instrument is the prima, which is tuned E-E-A. Sometimes the balalaika is tuned "guitar style" by folk musicians to G-B-D (mimicking the three highest strings of the Russian guitar), whereby it is easier to play for Russian guitar players, although classically trained balalaika purists avoid this tuning. It can also be tuned to E-A-D, like its cousin, the domra, to make it easier for those trained on the domra to play the instrument, and still have a balalaika sound. The folk tuning D-F♯-A is also used, as this makes it easier to play certain riffs.

Factory-made six-string prima balalaikas with three sets of double courses are also common and often use a "guitar" tuning. Although they are popular (particularly in Ukraine), they are generally considered to be inferior in quality to single course instruments.

The piccolo, prima, and secunda balalaikas were originally strung with gut with the thinnest melody string made of stainless steel. Today, nylon strings are commonly used in place of gut.

Tuning: E4, E4, A4 for Prima. A3, A3, D4 for the Secunda. E3, E3, A3 for the Alto. E2, A2, D3 for the Bass. E1, A1, D2 for the Contrabass. B4, E5, A5 for the rare piccolo.
Strings/Courses: 3/3 or 6/3
Further notes: Usually the Balalaika has 3 single strings, but there are also balalaikas with 3 double strings in unison courses. The double-strung version is more popular in the Ukraine, whilst in Russia they almost always have single strings. Usually steel strings, but sometimes a mix of steel and nylon for the Prima.
Scale Length: 430-440mm for the Prima. 480-500mm for the Secunda. 510-530 for the Alto. 740-790mm for the Bass. 1090-1190mm for the Contrabass.

and a MUST WATCH balalaika video of a great player and collector... BIBS.. with tips on how to play.... here

And useful Balalaika page here