The Choice column type is probably one of my favorites. A common use for it is within tasks, where the task status field is a choice of Not Started, in Progress, Completed, etc. I also use them for when I ask people to pick months or days if I want them as strings. The choice column lets you give the user some options to choose from, while making sure that all the options remain the same, so that later you can run reports on it.
One way I used to use choice columns was for Departments, but we have that covered through the Metadata column type now, so when wanting to work with Departments, please use the metadata, which will be covered in a subsequent post.
Here is what Microsoft has to say about the Choice column type:
Use this column field type to let people choose from a list of options that you provide. This column type is an ideal choice in cases where you want to ensure that all of the data in the column is consistent because you can limit the values that are stored in a column.
TIP: To limit the values in a column to only those values that are stored in the site, use a Lookup column instead of a Choice column.
You can customize a Choice column in these ways:
Define the list of choices Provide an exact list of values that people can choose. To provide this list, replace the sample text in the Type each choice on a separate line box with the values that you want. Type each value on a separate line. To start a new line, press ENTER.
Choose a display format Specify whether to display the choices in an expanding box, called a drop-down menu, or as a set of option buttons, called radio buttons, or check boxes. If you display the choices in a drop-down menu or as radio buttons, people can choose only one value from the list. If you display the choices as check boxes, people can choose more than one value.
TIP: If you want people to choose only one value and the list contains five or more choices, a drop-down menu is typically the best format.
Enable additional custom choices To allow people to enter a value that is not included in the list of choices, turn on fill-in choices. Doing so is a good idea if you may not know all of the values that people need to enter about items. If you prefer that people use only the values that you specify, turn off fill-in choices.
Display a default value Automatically select a specific value when someone adds a new item, while also allowing people to choose a different value if they need to do so. A default value helps people enter information faster. For example, if the column stores the names of companies assigned to a project and your organization works with a specific company for most projects, you can enter the name of that company as the default value. As a result, the company name appears automatically when a new project is added to the list, and team members do not have to choose the name.
A default value can be either a value that you specify or the result of a calculation, which is called a calculated value. Calculated values are helpful when you want to display specific text in the column automatically but the text might vary depending on who added the item, when the item was added, or other reasons. To use a calculated value, you enter a formula, instead of specific text, as the default value. The formula can calculate a value based on information in other columns or system functions such as [today], to indicate the current date, or [me], to display the name of the person who adds or changes the item.