A Long Aged Question: How is the content developed for the wireframe?

My name is Jarod, and I'm a web designer. Recently I started discovering that UX might most likely be my strongest field of interest since I'm most intrigued by how website visitors make buying decisions.

I was wondering though, and this has always been a question for almost a year now: whose job is it to develop the content, how is it developed, and (most importantly) how is it shaped into the wireframing process?

I always wanted to know this mainly because, if you're familiar with the "content is king" saying and its impact on web design, you may be aware that for a long time people previously used Lorem Ipsum as filler-content in their mockups. Some web designers still do it, but my biggest question of this all is how is the actual content developed into the wireframing process? I too would like to be able to design a website with real content some day.