Fe plus S equals FeS?

Yes, if the iron ion is iron(II), which means it has a charge of 2+. FeS is called iron(II) sulfide. If the iron ion is iron(III), with a charge of 3+, then the formula unit would be Fe2S3, and would be called iron(III) sulfide.
Yes, if the iron ion is iron(II), which means it has a charge of 2+. FeS is called iron(II) sulfide. If the iron ion is iron(III), with a charge of 3+, then the formula unit would be Fe2S3, and would be called iron(III) sulfide.