Use Platform Associations to connect objects together. When editing an object, you can treat an association like a field, so you can attach objects together to store more complex data than just the basic field types.
For example, say you have a Region object:
You could associate it to the Employee object. This will allow you to set a region for each employee:
Because a Region is an object (not a field), you can create as many fields as you like on it. For example, a Region could store a name, address, contact information, and so on - all of which will now be associated with the Employee.
You can also have associations that work through other associations. For example, say you have a Job object, which stores a Job Code, as well as other information about the job, such as its charge out rate. You probably have lots of different job codes, but you know they are unique by Region. You want managers to choose a job code on each worked shift. First, associate the Region to the Job:
Then, on the Worked Shift object, associate both the Region and Job. Set the Job association to work through the Region association:
When editing a timesheet, you'll initially see all Job codes available:
But if you select a Region, only Jobs in that Region will be selectable:
If this isn't working as expected, confirm that the API keys on your associations are consistent across all your objects.
If this is a sensitive association or linked file, you can also adjust who can see and edit this link by using the Visible To and Editable By fields. This will allow you to define which roles within your organization are allowed to view, add, or remove these associations.