Arial

Arial is a sans-serif typeface in the neo-grotesque style. Fonts from the Arial family are included with all versions of Microsoft Windows after Windows 3.1, as well as in other Microsoft programs, Apple's macOS, and many PostScript 3 printers. In Office 2007, Arial was replaced by Calibri as the default typeface in PowerPoint, Excel, and Outlook. The typeface was designed in 1982 by Robin Nicholas and Patricia Saunders, for Monotype Typography. It is metrically compatible with Helvetica, enabling documents to use either typeface without affecting the visual layout. Because of their similar appearance, Arial and Helvetica are commonly mistaken for each other.

From the Wikipedia article “Arial”, licensed under CC BY-SA 4.0.

Sans-serif faces work well for headings, captions, children's books and modern nonfiction. For long-form body text in print, most designers still prefer a serif.

Commercial typefaces require a licence that covers embedding in PDFs and ebooks; check the foundry's licence before you publish.