Question: I'm looking into Red Orchestra 2 (<http://store.steampowered.com/app/35450>) and am hearing great things. However, on Steam there is no singleplayer tag, and no reviews mention singleplayer. Is the product linked above a multiplayer only game or is there singleplayer as well?

Answer: 
There is a single-player campaign, but it's little more than a collection of tutorials and bot matches. To my knowledge, there isn't any story beyond "the fighting advances here!".
The single player campaign is a series of multiplayer matches with bots and no other players, hosted on a server ran on your own system.

If you want to play the campaigns itll run like an online game but with a lower FPS as the server it runs on is being hosted on your PC.

Incidentally, you can also play the campaign in online multiplayer, which is pretty cool. Find a dedicated server for it, join, and you can partake in a multiplayer campaign mode!