Determine your requirements
For the most part, you can create any kind of field that Joomla offers. Consent will generally have 2 or maybe a few options (including the option to decline). An example of a multiple option consent might be newsletter frequency. You might offer your user Annual, Monthly, Weekly, or No Newsletter. It's up to you to comply with these values using whatever software or method you're using to send the newsletters. These fields hold data - how you act upon that data is up to you.