It really depends on the conference. Contact the chair and speak to your colleagues to ask what benefit you might gain from attending the conference.
Some conferences, though in my experience in the humanities and social sciences, just ask for an abstract (a few hundred words) outlining the contribution of the intended talk. In those conferences, they pick which talks to have based on the abstracts. Then, after the conference, they invite a number of the best talks to write up their work as an article to be published in a journal.
In my field, computer science, most conferences require you to write a whole paper (usually 4-10 pages, depending on the conference and the size of your research contribution) to be able to give a talk at the conference. As @JenB says, most academic institutions will only pay for their research staff to go to a conference if they have published a paper there.
Now, some of the conferences that require a whole paper, will require an abstract to be submitted a week or two before the paper deadline. This is normally for logistical reasons, so they can pre-allocate which reviewers will review each paper.
Why might one want to go to a conference? To learn about the state of the art in this research field, and to network with the other researchers in the field, to maybe form collaborations.
Why might a researcher want to publish and present at a conference? To disseminate their work, get feedback from their peers, to promote their institution, and also for the reasons above.
Why might a employee of a company want to present at a conference? (I've not been in this situation, so take with a pinch of salt!) To disseminate their work (as much as their company allows), to promote their company, and also for the reasons above.
Why might an academic conference want industry attendees and presenters? To help cross-pollinate the work of academia and industry, so they can both learn from each other. To enable networking and industrial collaborations. To facilitate partnerships that might bring industrial money into academic research projects, or gain access to research council funding that requires industrial collaboration.