p38 is a type of mitogen-activated protein kinase (MAPK) that plays a crucial role in cellular responses to stress, inflammation, and apoptosis. It is activated by various stimuli, including cytokines and environmental stressors, and is involved in regulating gene expression, cell differentiation, and survival. In the context of cell signaling, p38 MAPK is part of a larger family of MAPKs, which also includes ERK and JNK. Its activation can lead to various physiological responses, making it a target for research in diseases such as cancer and autoimmune disorders.