The right fielder covers the right portion of the outfield grass (when viewing the field from home plate).
On defense: Right fielders are not required to have as much speed and range as center fielders. However, they often need to possess the strongest throwing arm in a team's outfield group in order to throw from right field to third base when baserunners attempt to advance from first to third on a hit to right.
On offense: Quality defensive right fielders are easier to find than top defensive options at center field, shortstop and catcher. Therefore, right fielders typically have to provide more offense in order to deliver all-around value. Many clubs prefer their right fielders to excel at providing power and reaching base with regularity.