Meristems are regions in plants where cells continuously divide and differentiate, allowing for growth. They are primarily found in areas such as the tips of roots and shoots, known as apical meristems, and in the cambium layer, which contributes to the thickness of stems and roots. There are two main types of meristems: primary meristems, which are responsible for the vertical growth of plants, and secondary meristems, which facilitate lateral growth. These specialized tissues play a crucial role in the overall development and regeneration of plants, enabling them to adapt to their environment.