Actually I think, the question refers to the priority preference during nomenclature of hydrocarbon containing both carbon-carbon double bond #(C=C)#and carbon-carbon triple bond #(CequivC)#.
The general rule is that any unsaturation #(C=C) or (CequivC)# to be preferred during placing locants (numbering) i.e to have minimum locant.
But if both #(C=C) or (CequivC)# occupy same position counting from opposite ends then #(C=C)# to be given minimum locant and 'yne' suffix for #(CequivC)#. is always followed by 'en' suffix for #(C=C)# to be added after the stem/root name.
Example
1.#stackrel(6)CH_3stackrel(5)CH=stackrel(4)CHstackrel(3)CH_2stackrel(2)Cequivstackrel(1)CH#
Here the unsaturation #(CequivC)# gets minimum locant if numbered from right. So the name becomes, #"hex-4-en-1-yne"#
2.#stackrel(6)CH_3stackrel(5)Cequivstackrel(4)Cstackrel(3)CH_2stackrel(2)CH=stackrel(1)CH_2#
Here the unsaturation #(C=C)# gets minimum locant if numbered from right. So the name becomes, #"hex-1-en-4-yne"#
3 . #stackrel(1)CH_2=stackrel(2)CHstackrel(3)CH_2stackrel(4)CH_2stackrel(5)Cequivstackrel(6)CH#
Here bot the unsaturation #(C=C) and (CequivC)# get minimum locant(1), if numbered from left and right. Here the preference should be given to #(C=C)# and numbering from left will be correct.
So the name becomes, #"hex-1-en-5-yne"#
