In SharePoint, a cascading list is a feature that allows you to create a relationship between two lists, where the values in one list control the values available in another list. This is particularly useful when you have a parent-child relationship between the items in the lists.

To set up a cascading list in SharePoint, follow these steps:

Step 1: Create the Parent List

1. Go to your SharePoint site.
2. Click on “Site Contents” or “Site Settings” (depending on your version of SharePoint).
3. Click on “New” to create a new list.
4. Select “Custom List” or “List” from the options.
5. Name your list and add any desired columns that you want to use as lookup fields in the child list. For example, if you’re creating a cascading list for countries and cities, the parent list could be “Countries” with a column called “Country Name.”

Step 2: Create the Child List

1. Follow the same steps as above to create a new list.
2. Name your list, e.g., “Cities.”
3. Add any columns you need for additional information about the cities (e.g., population, area, etc.).
4. Create a new column (e.g., “Country Name”) that will be used to link this list to the parent list. Set this column as a lookup column that looks up values from the “Country Name” column in the parent list (“Countries”).

Step 3: Configure the Cascade Relationship

1. In the “Cities” list, edit the “Country Name” column.
2. In the column settings, set the option “Get information from:” to the “Countries” list and select the “Country Name” column as the source column.
3. Optionally, you can choose to filter the values based on other columns in the parent list, e.g., if you have a “Continent” column in the “Countries” list, you can filter the “Cities” list to only show cities in the selected continent.

Now, when you add or edit an item in the “Cities” list, the “Country Name” column will display a drop-down list with the values from the “Countries” list. The available options will be limited based on the selection in the parent list, creating a cascading effect.