According to Russian legislation all foreigners* who are going to visit Russia have to receive Russian visa.
To get russian visa foreigners have to receive invitation. There are two kinds of invtations, they are tourist invitation and business.
Tourist invitation (tour. voucher) includes
- document that prooves that you were invited in Russian
- depending on tourist wishes it may be single our double entry voucher (visa consequently)
All these data give you an opportunity to receive russian tourist visa**.
*Except the countries, Russia has the reductive entrance regulation with.
**The validity period of time for tourist russian visa is up to 30 days.