Conditions create rules that will show or hide an option based on the customer's previous selections. With conditions you can, for example, show an option only if another specific option is selected.
When creating an option in an option set, you can add to it conditions.
To assign a condition to an option
Browse to the option set, and to the option you want to add a condition to, click that option to expand it
Scroll to the Conditions section and expand it by clicking it
Click Add Condition
Complete the condition's rules
Select action Show / Hide
When select option (the option that will generate the condition)