A larger sensor size generally indicates better image quality.
There are many types of image sensors ranging from a 1/2.5” to a full frame 35mm sensor. Other popular sensors are the Four Thirds and Micro Four Thirds sensors. The Micro Four Thirds sensor uses a mirrorless system that improves portability while a Four Thirds is generally larger in size.
The shape and size of the image sensor determines the angle of view of the particular lens attached. The angle of view is what the sensor can ‘see’ through the lens, so it determines the quality captured in an image.
Many camera brands have their own sensor size such as the Nikon CX sensor and Canon APS-C sensor.