Biofilms are highly organized, surface-attached microbial communities embedded within an extracellular polymeric matrix that enhance microbial survival, adaptability, and ecological success. Originating over 3.4 billion years ago, biofilms represent the dominant mode of microbial life and provide cells with protection from environmental stress, antimicrobial agents, and host immune responses. Biofilm development proceeds through sequential stages, initial attachment, irreversible adhesion, microcolony formation, maturation, and dispersion. Each regulated by complex molecular networks involving quorum sensing, second messengers such as c-di-GMP, and stress-response pathways. The biofilm mode of growth supports metabolic cooperation, efficient nutrient retention, and elevated horizontal gene transfer. Biofilms play critical roles across natural ecosystems, industrial systems, and clinical environments, contributing to both beneficial outcomes (e.g., wastewater treatment, bioremediation, plant growth promotion) and detrimental effects such as biofouling, corrosion, and persistent infections. Understanding the structural, molecular, and functional aspects of biofilms is essential for developing effective strategies for their control and harnessing their potential in environmental and biotechnological applications.