A stroker is an engine that has had its crank stroke modified. They can be increased (stroked) or decreased (de-stroked). Short stroke engines build rpms faster and can sustain higher rpms because there is less reciprocating mass. Longer stroke motors have greater rotating mass and therefore have greater torque. This is a general answer, there is more to it but enough for now.
A 383 is a 350 block which uses a 400 crank made with main journals to fit the 350. It makes very big torque numbers almost at idle and therefore is great for a street motor which has to move a heavy car quickly or a light car very quickly. Lots of people build them because they only cost about $200 more than a rebuild using stock parts.