When the wind is coming from the side, you are on a reach.  Let the sail out until it starts to luff and then pull it in just enough so the luffing stops.  If the wind shifts, adjust the sheet.   Most boats sail fastest on a reach.

beam reach - wind across the beam

close reach - wind comes more from front than a beam reach.

broad reach - wind comes more from the back than a beam reach

beam - width across the boat