MAPKs, or Mitogen-Activated Protein Kinases, are a group of proteins that play a crucial role in transmitting signals within cells. They are involved in various cellular processes, including growth, differentiation, and response to stress. MAPKs are activated by a series of phosphorylation events, which are chemical modifications that turn the proteins on or off. There are several types of MAPKs, including ERK, JNK, and p38 MAPK, each with specific functions and pathways. These kinases help cells respond to external stimuli, such as hormones or environmental changes, by regulating gene expression and other cellular activities. Their proper functioning is essential for maintaining normal cellular processes.