To reboot a computer (or a phone, a router, any machine with software in it) is to turn it off and start it again, so that everything loads fresh from the beginning. The word works two ways with no change in form. You can reboot the machine — 'I rebooted my laptop' — or the machine can reboot by itself — 'the laptop rebooted' — and nobody says 'the laptop was rebooted by me' unless they are being very formal. It is also a noun: 'the phone needs a reboot'.

This is the ordinary word IT people and normal people both use. 'Restart' means almost the same thing and is a bit gentler and more everyday; 'reboot' sounds slightly more technical, and a little more like you are taking the machine all the way down to nothing and building it back up. In practice most people treat them as the same. There is an older, stronger sense some technicians keep: a 'cold reboot' means cutting the power completely, a 'warm reboot' means telling the software to restart itself. Most speakers never make that distinction.

The interesting part is where the word has travelled. Films and TV series get rebooted now: someone takes an old story, throws away what came before, and starts it again from the beginning with new actors. 'They're rebooting Spider-Man — again.' That is now probably the second most common use of the word, and younger people meet it there first. And from there it has stretched further, into life: 'I need to reboot my career', 'after the breakup she rebooted'. That last use is loose and a bit fashionable — it borrows the feeling of a machine wiping itself clean and starting over, which is of course not really what happens to a person. Older speakers sometimes find it silly. It is common enough that you will hear it every week.