Salesforce picklist option values are set to “Restrict picklist to the values defined in the value set” by default nowadays.
If you want to integrate the options with a third-party system, you probably need to copy the Salesforce picklist value into another system for reference, otherwise, the record may not be able to create in Salesforce due to wrong picklist option value.
How to copy the picklist values? [Information for new users to Salesforce]
1. Slow: value one by one…
2. Brute force: view HTML source code, get the option values
2.1 Salesforce classical user interface only
2.2 May not getting the full option value, since options are depending on record types.
3. In the field Admin page, click “Print View”, if you don’t have admin access, ask your administrator to do it for you.
Hope this helps…