In structural applications, mechanical and structural effects introduce stress or strains onto polymers and polymer composites. Micro- and macro-sized fractures in the material are brought on by these effects. In order to fix these damages, which have a substantial impact on the material's lifespan and durability, self-healing materials inspired by biological systems have been developed. Both autonomous and non-autonomous recovery mechanisms have advanced quickly, particularly in the last several years. With thermoset and thermoplastic materials, which are widely used in industry, both molecular and structural approaches are applied. This study describes mechanisms and strategies of self-healing.