Stroke is a term which has multiple meanings within the sport of rowing. It is used to refer to the action of propelling the boat with oars, to a rower seated in a particular position and to one side of the boat.
The stroke is the set of actions to propel the boat, and comprises two main parts - the drive when pressure is applied through the oars to pull the boat through the water, and the recovery when the oars are lifted out of the water and returned to the start position. 
When the boat has more than one rower, the rower closest to the stern of the boat is referred to as "Stroke". This is the most important position in the boat, because the stroke rower sets the stroke rate and rhythm for the rest of the crew to follow. Stroke seat has to be a very calm and yet very competitive individual. A good stroke will lead a team by bringing the best out of every rower in the boat. The rower at the opposite end of the boat is referred to as bow.
Stroke side refers to the port side of the boat, which is on the left-hand side of a cox facing forwards, but on the right-hand side of a rower facing backwards. The usage derives from the tradition of having the stroke rower's oar be on the port side of the boat. However, the stroke seat oar in a sweep boat does not always emerge from port side in instances such as when the boat is starboard rigged