What is Medline?
Is a citation database started by the National Library of Medicine in the 1960s. It has citations of over 5200 journal titles from around the world in about 40 languages and published from 1966 to present. It is the primary component of PubMed.
Here is more information: https://www.nlm.nih.gov/medline/medline_overview.html
What is Medline Ultimate?
It is a database that the Purdue Global Library subscribes to through EBSCOhost. It includes approximately 1,650 active full-text, non-open access journals (1,605 peer reviewed). The most comprehensive companion to Medline, Medline Ultimate offers the largest collection of top-tier biomedical journals, many with no embargo, to provide you with access to the information as soon as it is published. Medline Ultimate also includes Ahead of Print content for relevant titles from key publishers.
While it does have 3500 less journal titles than Medline, it is an excellent place to search and it's interface is easier to use than PubMed's.