Conditional questions in a form is a handy tool to do many things including making sections / questions in your form visible based on previous answers in a multiple choice field.
The below video will show how events work in a form:
In the field settings of the multiple choice question you can select the Events tab located right next to Properties, and you can see whether there have been existing events that have been created, depending on what is displayed in the blue link. You will be able to view what event is triggered, and then you can delete them if they are no longer needed.
On each field that is triggered by an event you will see the lightning bolt icon so that you can see what events are being triggered and to go back and make changes on the event if needed. This helps with troubleshooting any issues with your form flow to ensure that you have set it up as you intended it to.
The kinds of Events that you can create are Make Visible, Make Invisible, Must Answer, Becomes Optional and Set Value.
Make Visible: If you have a field of form section that is set invisible by default, but would like it to become visible when a specific answer is selected, then you can do this by selecting the answer that would need to be answered, and then drag and drop the Make Visible option to the field/section of the form that you would like to be made visible with that answer.
Make Invisible: If you have a field of form section that is set visible by default, but would like it to be made invisible when a specific answer is selected, then you can do this by selecting the answer that would need to be answered, and then drag and drop the Make Invisible option to the field/section of the form that you would like removed from the form.
Must Answer: This selection will make a field that was previously not required to submit the form, to be made into a required field. As above, simply select the answer that makes the field required, and then drag and drop the Make Answer option to the field in question.
Becomes Optional: This will make a field that was previously required to be filled, no longer required and free to be left unpopulated. Select the answer, and then drag and drop the setting to the correct field.
Set Value: This is where you can create a value that will auto-populate a field within the form with specific information when the related answer to the multiple choice choice question is selected. There is a field beside Set Value, where you can input the information that you would like to fill out the form field in question.