The examples of visa invitation letters (made through CAV) are shown below:
A simplified visa invitation letter (the inviting organization is St. Petersburg branch of Steklov Institute of Mathematics):
The invitation issued by Steklov Institute (usually for EU citizens). Note that dates and names may differ.
A translation of the invitation. You do not need to provide a translation. It is just for your understanding of the message.
A regular visa invitation letter (issued by Russian authorities, the inviting organization is Russian Academy of Sciences):
The invitation issued by the authorities (usually for non-EU citizens)
The translation of the invitation. Note that names and dates may differ. You do not have to provide the translation. It is for your understanding of the message.