Medline and PubMed are literature databases for medicine, nursing and other health disciplines. As both databases provide content from the National Library of Medicine, there is a great deal of overlap. Both contain citations to articles in English and other languages from 1942 to the present. New records are added daily. Both databases rely on Medical Subject Headings (MeSH) to describe the content of the articles and other publication types. There are significant differences, however, that will influence your choice. Medline and PubMed use different search engines with varying degrees of user friendliness. The content of Medline includes 22 million citations from more than 5,600 journal titles. Citations as they are received by the publisher are entered into the Pre-Medline database and then moved to Medline when processing of the record is complete. PubMed includes 25 million records for articles, books (NCBI Bookshelf), author manuscripts, and all journals in PubMed Central, an open access journal repository. PubMed can also serve as an access point to the genetics data databases offered by NCBI. Citation records that require processing are included in PubMed; there is no separate database requiring searching. Finally, Medline is a University Libraries subscription so access will come to an end when you graduate. PubMed is freely available to everyone.
Here are some suggestions for your search strategy:
Ovid provides a comprehensive 30 minute tutorial on the use of Medline. There are several sections so feel free to choose what you want from the left sidebar. https://www.brainshark.com/wkovid/vu?pi=zGizVDdlez34XJz0&cmpid=Brainshark:MedlineIntro
The National Library of Medicine offers a comprehensive collection of tutorials, videos and handouts to support users of PubMed. https://www.nlm.nih.gov/bsd/disted/pubmed.html
There is also a YouTube channel to consult. https://www.youtube.com/playlist?list=PLBD13A2628C7A9965