If you've ever opened a PowerPoint presentation on a computer other than your own, you may have seen the text get all messed up.
This happens when you use fonts on your own computer that aren't installed on the computer you present with. PowerPoint will then substitute your font for another. Sometimes it still looks OK, other times the spacing of the text gets completely ruined and your presentation looks amateur.
To avoid this, embed the fonts you use in the file along with your presentation.
In PP for Windows, go to File > Options > Save, then scroll down and check "embed fonts in file"
On a Mac, go to Preferences > Output and Sharing > Save, then under Font Embedding, select "embed fonts in file".