For questions you should post in Q&A section.
Anyway, Gapps is Google Apps, this is the package that include Google's apps.
Some ROMs have the gapps included in ROM's zip, but other ROMs you should download the gapps separately, and flash it after the ROM's zip.
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Galaxy W / Monster v14 by ipromeh / Skull kernel v1.8 + Odexed + Greenify