When you are creating a (custom) Field for your database, you have a few choices for the Input Type.
Outlined below, is a brief description of each available type of field which you can create, and an example as to how that type of field appears when you are coding.
Pick a date using a drop-down calendar. Since the dates are not added until the time of coding, you don't need to add any values.
Enter any text you choose into a blank. Since it's freeform, you don't need to add any values.
A list of values to choose from, plus an "Add New" option for when your value is not (yet) in the list.
A list of values without an "Add New" option.
Freeform field that expands to display longer inputs. Since it's freeform, you don't need to add any values.
A list of values to choose from, allowing a user to select more than one applicable value. Type in a value, then click Add. Click the to delete a value. Click Done/Close when you are finished.
WHEN UPDATING A PICKLIST: Be considerate of any potential Bulk Actions you will need/want to make, as Bulk Actions for Picklist type fields will overwrite any existing selections for that field.
For example, if you were to select a series of documents tagged with the Gable Enterprises and Smith Industries values of an "Contract" picklist type field, and then make a Bulk Action to mark all documents with the Contract "Zephyr Unlimited" value, all selected documents would then only be tagged with the Zephyr Unlimited value.
Set a single value.