When saving records in Operate - whether they are leads, accounts, licences, etc. - the system will ask you to provide data in a set of mandatory fields. The record will not save, unless those fields have been populated.
Mandatory fields are marked with an asterisk (*) sign all throughout Operate. Fields without the asterisk are not mandatory.
If you want to choose whether a particular field is mandatory or not, you can do so by customizing the standard fields on the module that the field belongs to.
Each Operate module can be customized under Settings > General > Customize.
Choose the module that your field belongs to, then select Standard Fields. Find the field you want to configure, edit it and check or uncheck the Required checkbox. Save your changes when ready. Read more about Customizing Standard Fields in Operate.
This process is generally applicable, for any Operate module, with a few exceptions.
Modules where Standard Fields cannot be customized:
Let's assume you do not require the 'Industry' field that is set as mandatory when saving a Lead. To make this field non-mandatory, follow these steps:
Go to Settings > General > Customize > Leads > Standard Fields. (where Leads is your module)
Search for the 'Industry' field and select it.
Check/uncheck the Required checkbox in order to enable/disable the field to always require a value in order to save a record.