Inline elements have fewer layout properties associated with them; they are meant to sit alongside the content that precedes and follows. . Most inline elements are text-related. The big exception is images.
span tag is a catchall inline tag. It's used primarily when there is nothing in particular of note about the content; the span tag is used to alter the layout in some way.
codetag is there to demarcate code snippits
hreftelling the link where to go. Links can be absolute (full url) or relative (if a local project).
srcattribute with a location of the source (relative to your server or absolute link). This image is pulled in from John's website: