Schema markup is structured code added to your website that explicitly tells Google what kind of business you are, what you offer, and where - rather than making Google guess from the visible text alone. For remodelers, the schema types that matter most are LocalBusiness (or a trade-specific type like HomeAndConstructionBusiness), plus FAQPage schema on pages that answer common questions.
You don't need to understand the code to benefit from it - a properly built website should have this wired in automatically. What's worth knowing as a business owner: schema is one of the reasons a rich, detailed FAQ section on your pricing or service pages does double duty, helping both human visitors and Google understand exactly what you offer.