Q1: Why are readme's in github in the .md format? What is .md and why does github use it instead of .txt, .html .docx, or any other file format?

The markdown format allows the user to control the display on the document. It is also an easy-to-read, easy-to-write syntax for formatting plain text format. ".md" stands for markdwon and used instead of other text heavy documents because there are no special tags to remember (like in HTML) but it can be implement HTML tags. Word documents likes ".docx" will need to used function within the application in order to format the text that does not leave any direction from the web browser or that it cannot be read by it.

Q2: Is the keyword "fixes" the only way to auto-close an issue from a PR (pull request). Is there other keywords that can accomplish the same thing? As per githubs website, you can also use "close, closes, closed, fix, fixed, resolve, resolves, resolved". When in the discription or comment of the pull request, you will add one of the keywords and the issue number together. When the changes have been accepted and merge, it will close the issue and you also have an option to delete the branch as well.

Q3: Do you have to create a new PR EVERYTIME you want to close an issue, or is it possible to close multiple issues within a single PR? If so, how? No, you do not need to do a new PR everytime you want to close different issues, you can use the keywords and issue number in the discription.