A created in a table can be used in formula-columns, in documents, in workflow actions, in filters of database objects (for example, views, triggers, buttons etc.) and in the other database functionality like relations, form behavior, table record access etc.
If you need to know where the column is used, just review the Column Usage section displayed below the Column Properties form.
To open the column properties form and the column usage section:
Click the Setup link at the top right corner of the window.
Select a table you need.
In the list click a necessary column name.
As the result, the will be displayed and below this form you can notice the Column Usage section. In this section you can see names and types of objects and features where the column is used. Furthermore, you can click on a name of the object or feature to find the column in the settings of this object/feature.
In addition, when you need to delete the column, the Column Usage section is shown on the Confirm Deletion screen. So, you can see which objects/features can be damaged after the column deletion.