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A new account needs Steem Power, which can also be delegated. For registrations on steemit.com, Steemit Inc. pays that, and takes it back after a while.
Steeminvite enables users to do that themselves if they don't want to wait for the account to be activated.

I see. Thanks for the explanation. It makes sense now. I will try to promote it to my friends. :)

意思是steemit官方创建账户也是要花steem的,所以要排队审核。
但自己出steem就可以很快创建成功了?

如果用他们的网就可以不要排队。但要自己马上付。

Currently the way the STEEM blockchain is designed requires a fee to create new accounts. If you sign up via steemit.com the fee is paid by steemit. Anyone who already has an account can create an account for someone else using the CLI Wallet or with steemconnect but you need to pay the fee.
This is another tool that enables steem users to create accounts for others.

Cool. Thanks for the explanation. Appreciate it.