Repellents are substances designed to keep pests, such as insects and animals, away from people, plants, or areas. They work by creating a barrier that either masks scents or emits odors that are unpleasant to the pests. Common types of repellents include those made from natural ingredients, like citronella and eucalyptus oil, as well as synthetic chemicals like DEET. These products are widely used in outdoor activities, gardening, and pest control. They can be applied as sprays, lotions, or candles. While repellents can be effective, it's important to follow usage instructions to ensure safety and effectiveness.