Having the loft and lie angles checked and adjusted if necessary is a relatively inexpensive tune-up that'll save you strokes and some headaches. Both loft and lie angles are static measurements that change over time of use. Especially if you hit off of a mat covering concrete.
Loft on your irons is set by the manufacturer and there should be about a 4 degree difference between each club for 5 - SW, and around 2 - 3 degrees for long irons. This should result in about a 10 yard gap between each club. When set properly it results in correct trajectory and distance control.
Lie is a measurement that is taken in normal playing position with the center of the sole touching the ground. It affects the direction and the flight of the ball. Too flat and the ball goes to the right of the target. Too upright and the ball goes to the left of the target (based on a right handed golfer).