The masthead, in publishing, is the imprint information, usually found either on the front cover, or the first inside page. It includes editorial information about the journal - its name, its editor or editorial board, the location of its offices, etc. Online, this may be accompanied by information about the publishing scope of the journal.
The editorial board refers to not only the "editor-in-chief," but also the group of people, usually academics who are experts in the field, who select the articles for publication. They may also be, but are not always, the peer reviewers. Members of the editorial board may also write brief editorial pieces for the journal, and often are responsible for selecting themes for special issues. They may also reach out to other experts to solicit articles if deemed appropriate.
Journal name: The name of an academic journal will often be explicit and clear - it will immediately indicate to the reader the scope of its contents. Examples include The Journal of Mental Health, The Journal of Business Ethics, or Higher Education. Some journals names include the word journal, but not all. In an APA 7 citation, the journal name is always in italics.
Volume: The volume usually represents a year's worth of publications for a journal. Some journals are quarterly, while others are released with much more frequency and may be monthly or even weekly. In instances where print journals are retained, the issues for one year are often bound together in a single book or...you guessed it, volume! In an APA 7 citation, the volume number appears italicized following the journal name, separated by a comma.
Issue or Number: The issue or number represents when within a volume the article appears. If a journal is printed quarterly, for example, the issue 2 maybe represent its summer issue. If it is printed monthly, 11 would represent November. The issue or number is indicated in an APA 7 citation following the volume number, within parentheses, without a space between them.
One thing that may not feel clear to you is why there is a focus on academic journals instead of books. If you have watched television shows or movies set on university campuses, you likely have seen a lot of footage of students or professors sitting in a big, dark library, poring over big heavy books. Then, you start university yourself, and all your professors talk about articles and journals!
Journal articles allow scholars to publish relevant research more quickly, and in "smaller" pieces. In many cases, books are used to group together research from a variety of scholars on a a much larger subject that we would see in a research article. For example, an article might focus on understanding the role of library anxiety in the academic success of first year international undergraduate students, but if that research were to be published as a chapter in a book, the book itself might be called simply Library Anxiety, and include chapters on research like how first year experience librarians can mitigate library anxiety or the usage of the library by graduating undergraduate students and their likelihood of applying for graduate studies. As you can see in the examples I've given, all three of the "research topics" relate to Library Anxiety, but would exist as chapters in the book! In some cases, journal articles are expanded on and published as a chapter in a book later.