Apple Keynote is a free software included in your Mac, very useful to make professional presentations and slideshows. Pick a ready graphic template, and start creating your own slides, by adding text, charts, tables, shapes or your own media on each of your slides.
The slide template allows you to make a clean and organized slideshow even if you start from a beginner level. Then customize all your elements by adding special contours, filling, shadow, transparency and reflection. If you import a video or a picture, you can directly crop, size and apply corrections on its appearance.
Keynote also has the ability to apply great transitions to your slides, and effects to each of your slide elements to make your presentation awesome.