Manufacturer shutter actuation ratings are the number of actuations to which the shutter has been tested. Many will go far beyond this tested number. Some may fail early on for whatever reason.
A camera’s shutter count can give a general estimation of how much the camera has been used but should not be considered the sole deciding factor on whether or not to purchase a used camera.
Manufacturer tested shutter ratings generally range from 100,000 to 300,000 actuations depending on the model.
Many shutters will surpass these ratings.
Many other factors can have an effect on a camera’s lifespan. How it was cared for, whether it was serviced or not, storage conditions, etc.
Not every camera records the shutter actuations and some will reset this number if the camera's firmware is updated.
The shutter count can often be difficult or not possible to retrieve and 3rd party software that can extract the count is not necessarily reliable.