The Bolshevik Centre was a select group of Bolsheviks that led the organization in secret. The Centre conducted its activities in secret in part so as to avoid the prohibition by the Russian Social Democratic Labour Party ("RSDLP") on separate committees outside of the RSDLP.
The Bolshevik Centre was headed by a "Finance Group" consisting of Vladimir Lenin, Leonid Krasin and Alexander Bogdanov.
References
Bolshevik Centre Wikipedia(Text) CC BY-SA