If you're concerned about it, you can open it, select all, and delete the contents.
But I suggest you have a look at it first. There's no real mystery.
You see what sites are entered. If the site is beside the entry "127.0.0.1", it means that attempts to reach that site are redirected back to your own computer, or effectively blocked.
For example, here are my entries that prevent redirection to some 'doubleclick' sites:
127.0.0.1 localhost
127.0.0.1
www.doubleclick.net
127.0.0.1 ad.doubleclick.net
127.0.0.1 m.doubleclick.net
127.0.0.1 phase2media.doubleclick.net
Now, some malware might add something like:
(google IP address) (malware IP address)
that would redirect Google to its own site.
If something is unknown, you can do a'Whois' search by IP, or just delete the entry.