The right back in soccer is a fullback position that is known as a defensive spot. According to Expert Football.com, the right back or right fullback is positioned on the right side of the stopper or center fullback. The right full back has a wide variety of responsibilities on the soccer field and learning the nuances of the position can take some time and practice.
Cover the space to the right of the center fullback on defense. Expert Football.com says that the right fullback must cover the space along the entire flank and be fairly fast.
Mark or cover an opposing forward if they are in your area. Soccer Training Guide says that marking the forwards is your main task and that the right back's focus is defense and you must sacrifice your offense for defense.
Run and push up the field to help on offense when it is required. Expert Football.com says that right backs get actively involved offensively by staying wide and making overlapping runs to spread the defense apart. Basically, the fullback sometimes adds in on the offensive side during aggressive plays as an extra player for the other team to worry about.
If you want to punch up your game, spend time watching video of the great professional right backs like Dani Alves and Sergio Ramos.
Keep up with your practice drills so your moves, speed and agility improve with every game.