I have a question mark when I turn on my Mac. I tried pressing command + R at start up but after about 2-3 minutes of white screen the question mark reappears again. What can it be and what do i need to do?

Command-R only works on Macs whose recovery partition was installed when 10.7 or later was installed.

You can try to see if there is a bootable partition by holding down just the Option key at startup.

If there is not, then you probably have a damaged hard drive. Sometimes it is only the directory, sometimes it is the drive itself.

If you are lacking a backup, please read this tip:

My data has become inaccessible, and I don't have a backup!