The Board and card games gaming genre is one of the easiest genres to identify out of all different PC video game subsets that exist. Simply put, any game that is played on a traditional board offline that is converted into a PC game will fall into this category as well as any game that is played with cards. Placing aside the obvious definitions, the board and card game genre is actually one of the widest in existence online.
Part of the reason for the prevalence of board and card games is that newcomers to the internet and those looking for a simple game flock to the genre. It does not take a lot of expert skill to master these games and pretty well everyone of every skill level will enjoy the games which is why PC creators continue to develop board and card games, because they know there is a large populace that will flock to their creations.
In fact, every PC already has one game at least installed with Windows upon purchase that you will instantly recognize, Solitaire. However, there is more to the attraction of the genre than just simplicity.
One reason that board and card games flourish online is because the internet provides for multi player forums and games. Online poker in both its free and paid formats is very popular because not everybody has a group of friends to play with Saturday night. Along the same lines, some people enjoy board games, but most require a team of players which is easily found if you head online to play.