Tank and Spank is the most common type of PvE fight. Tank holds aggro, DPS nuke the mob(s), healers keep the tank alive. The only common complication in fights of this type is aggro - damage dealers must be careful not to generate more threat than the tank.
The expression is sometimes used derogatory, meaning that a boss is very easy to beat (or needs only a minimial amount of tactics or positioning to beat, such as avoiding a very visible and avoidable AoE). If such a boss is still tough (because he deals large amounts of damage), it's called a Gear Check.
Examples: Attumen the Huntsman, Patchwerk