Dedicated IP address
A dedicated IP is a feature offered by an email service by which you can send out all your mailings from just one specific IP address. In this case, no other users will be sending emails out from this address. This will have a positive impact on the reputation of your mailings, as well as on the percentage of emails opened and the number of conversions.
This is generally something that mailing list services provide for an additional fee, or it is activated for free at higher rates.