They answered the question better than I could, but yes, it's an app for android/iOS that drops you as a "runner" gathering supplies and completing missions in a fictional zombie apocalypse. I used the c25K one and main app, went from zero running ability to doing a half (slowly but successfully) during didactic part of school.
It's a really fun plot, a good amount of variety in your "missions" and the characters are quite memorable. I think it was partially the test-induced sleep deprivation I was running through, but I distinctly remember breaking into tears at a particular plot point in s2, if that tells you how involved I got in it, lol. There's a lot of content available now, too, with race missions and training plans and whatnot.