The appearance of text makes a huge difference to any presentation. The font typeface used within your slides is dictated by the active Theme or Theme Fonts set of your presentation — you can certainly override these defaults and choose another font typeface and also change the font size. However, there are times when you need to highlight a word or a phrase contained within your text so that it stands apart and commands attention. To do so, you can apply font styling options that let you make your text bold, italics, underlined, etc.
Microsoft and the Office logo are trademarks or registered trademarks of Microsoft Corporation in the United States and/or other countries.