What is the difference between Investor and Altruist?

As I have unlocked the ability to place a Bounty, I have applied one to someone else's question, which earned me the Investor badge, description reading First bounty you offer on another person's question. Now, there is a badge that is confusing me, Altruist is another badge with the description First bounty you manually award on another person's question. So, in these two badges, what is the difference between the words "you offer" and "you manually award"?