When people give presentations, they sometimes use "slides". Slides are still images that you show, one after another, while you're giving a presentation.
Slides go in order. You can talk about different slides by explaining where they were in the order. The slide that you're looking at is "this slide" or "the current slide":
This slide shows how our manufacturing process works.
To descibe the one before the current slide, use "the last slide" or "the previous slide":
On the previous slide, you listed the number of unemployed workers in Europe. Where did that figure come from?
To describe a slide earlier than the previous one, use "an earlier slide" or "one of the previous slides".
Talk about slides after the current one with "the next slide" or "a later slide".