Plants have evolved a sophisticated immune system to combat pathogens, comprising two main lines of defense: pattern-triggered immunity (PTI) and effector-triggered immunity (ETI). PTI is initiated by cell surface pattern recognition receptors (PRRs) detecting conserved pathogen elicitors, while ETI is triggered by intracellular NOD-like receptors (NLRs) recognizing specific pathogen effectors. These two defenses work synergistically to enhance disease resistance and trigger a series of downstream defense responses. The interplay between PTI and ETI involves complex signaling pathways, including the generation of reactive oxygen species (ROS) and calcium ion influx, which serve as critical second messengers. Recent research has revealed that PTI and ETI are interdependent components of a unified immune system, with PTI priming the plant for a more potent ETI response. The crosstalk between PTI and ETI is further modulated by transcription factors and hormone signaling pathways, ensuring a coordinated defense against diverse pathogens. This review provides a comprehensive overview of the stepwise activation of plant endogenous immunity, focusing on the recognition of extracellular and intracellular effectors by PRRs and NLRs, and the complex interplay between these pathways.Plants have evolved a sophisticated immune system to combat pathogens, comprising two main lines of defense: pattern-triggered immunity (PTI) and effector-triggered immunity (ETI). PTI is initiated by cell surface pattern recognition receptors (PRRs) detecting conserved pathogen elicitors, while ETI is triggered by intracellular NOD-like receptors (NLRs) recognizing specific pathogen effectors. These two defenses work synergistically to enhance disease resistance and trigger a series of downstream defense responses. The interplay between PTI and ETI involves complex signaling pathways, including the generation of reactive oxygen species (ROS) and calcium ion influx, which serve as critical second messengers. Recent research has revealed that PTI and ETI are interdependent components of a unified immune system, with PTI priming the plant for a more potent ETI response. The crosstalk between PTI and ETI is further modulated by transcription factors and hormone signaling pathways, ensuring a coordinated defense against diverse pathogens. This review provides a comprehensive overview of the stepwise activation of plant endogenous immunity, focusing on the recognition of extracellular and intracellular effectors by PRRs and NLRs, and the complex interplay between these pathways.