Push notifications allow applications to communicate important updates, reminders, or alerts to users directly on their devices, whether mobile or desktop. They appear as alerts or banners and can include text, images, and action buttons to prompt users to interact. In the context of web3 and decentralized applications (dApps), push notifications serve as a key tool for enhancing user engagement by providing timely information about transactions, new offers, security alerts, and other relevant activities within the ecosystem.