Question

Can someone please explain to me what parsing XML means? And what does an XML parser do in general?

Answer 1

It means “reading” the XML file/string and getting its content according to the structure, usually to use them in a program.

For example if you have this XML fragment:

<root>
    <node1>value1</node1>
    <node2>value2</node2>
</root>

you may want to use these values in a data structure:

ClassRoot:
    node1: string
    node2: string

so that, in the end:

Object goofy = ClassRoot.new
parse(xml, goofy)
puts(goofy)

yelds something like:

goofy[node1='value1'; node2='value2']

There are many ways of doing so, like DOM or SAX.
You might want to investigate XSLT and xpath as well, according to your needs.