It is an network of internet connected devices are embedded in everyday objects and allows to send and receive data (settings, telemetry, etc.)

IoT Hub

Bi-directional communication with streaming source
Was designed specify to connect to IoT devices, sensors, etc.
Allows to manage security for individual devices
Gives Insight into the producer and consumers, allows to monitor and control the source
It is a PaaS (Platform as a Service) offering
Highly secure, scalable and reliable service
Provides SDK for lot of programming languages
Supports : AMPQ, AMTT and HTTPS

Azure IoT Central

Similar to IoT Hub but provides ready made templates that can be used to create services
It is SaaS (Software as a Service) offering
No deep technical knowledge required
Build on top of IoT Hub and 30+ other services

Azure Sphere

Provides Sphere MCU (Micro Controller Unit)
Provides Sphere OS on top of which we can make apps
Azure Sphere Security Service: Allows communication between the cloud and the device itself
Allows to build secure. end to end solutions

Azure IoT Edge

Allows to deploy services to Edge devices (IoT hardware devices)
Deployment to Edge devices are done using modules
Modules are Docker compatible containers
They are the smallest unit of compute managed by IoT Edge

To deploy module to IoT Edge Device a container needs to be created which needs to be hosted in ACR, an manifest file needs to be generated for the edge devices that tells them which modules needs to be installed