As you can see from the screen, alkynes have a triple bond - they are a group of hydrocarbons which only contain carbon and hydrogen and have triple bonds.
Alkynes also have the general formula CnH2n-2 which if you're unsure you can use to work out the formula.
In the case of butyne we can use the general formula Cn (n = 4); H = 2 x n (4) = 8 take away 2 = 6, so the formula (for butyne) is C4H6.
Alkynes all have triple bonds and similar chemical properties.