The equation Pb(NO3)2 + 2 KI is the left side of the equation for the reaction of lead(II) nitrate and potassium iodide. The full equation is written as Pb(NO3)2 + 2KI = 2KNO3 + PbI2, representing the products of the reaction as potassium nitrate and lead(II) iodide.
Pb is the chemical symbol for lead, N is chemical symbol for nitrogen, O is the chemical symbol for oxygen, K is the chemical symbol for potassium, and I is the chemical symbol for iodine. The symbols for each element can be found on the periodic table of elements. The numbers indicate the amount of atoms in each component.