Theme Fonts, Theme Colors, and Theme Effects are individual components contained within each Theme in PowerPoint – these influence how individual slides in your presentation look. Note that while all the slides differ in terms of colors, fonts, and effects applied, their text content is still the same. When you apply a different Theme to your PowerPoint presentation, the fonts, colors, and effects applied to your slides change. Unless you override this on a per slide basis, these changes show up in all slides in the presentation. The resulting slides all look consistent.