Here is a lookup table of HubSpot’s default contact properties.
I have been working on HubSpot data analysis with R on a daily basis and having a good understanding of contact properties can save me a lot of time. HubSpot provides the properties CRM api for developers to get the contact properties list and also provides the explanations of all the default contact properties: https://knowledge.hubspot.com/contacts/hubspots-default-contact-properties.