It indicates that you think the work is a meaningful contribution towards (but not a full solution for) the problem named by the paper title. I'm not sure if th

It indicates that you think the work is a meaningful contribution towards (but not a full solution for) the problem named by the paper title. I'm not sure if there's a distinct origin (see https://english.stackexchange.com/questions/188988/what-is-the-origin-of-the-towards-a-new-used-in-the-titles-of-some-research-ar https://english.stackexchange.com/questions/188988/what-is-t...), but it's fairly conventional these days.