A house primer is an essential preparatory coating applied before painting surfaces like walls, ceilings, or exteriors. It creates a smooth, uniform base that enhances paint adhesion and ensures a longer-lasting, high-quality finish. Primers also help to seal porous materials, block stains, and prevent color bleed-through, making them especially useful for new construction or when painting over darker shades. Choosing the right primer for the specific surface and environment is crucial for achieving professional results.