HubSpot has a very detailed article in their knowledge base if you want more details.
Here is an excerpt.
“The HubSpot calling tool allows you to call contacts from your browser or phone and log calls on your contacts’ timelines in HubSpot.
The number of calling minutes in your HubSpot account depends on your subscription. An alert will appear in your account when you’re within 100 minutes of your limit. If you reach your limit while on a call, you will be able to complete that call, but will not be able to make additional calls that month. Calling minutes reset on the first day of each month.
If a contact has opted out of all communication, you will need to give the contact a one-time legal basis to communicate with them before making a call. In the dialog box, click Give a one-time legal basis to assign a lawful basis and explain why you’re allowed to communicate with the contact. You will need to assign a lawful basis to contacts who have opted out of all communication even if the GDPR setting is turned off in your account.
If you have an assigned Sales Hub Enterprise or a Service Hub Enterprise seat, you can access the call’s transcript on the contact’s timeline after the call has been saved. The call needs to be recorded in order for it to be transcribed. The transcript will appear on the contact’s timeline as an attachment.”