Please explain

Okay here goes, all my life I was pretty much proud of my body, I could eat what I wanted when I wanted and I always stayed thin...Yes it was to good to be true!!! I am now 41 (42) and I am 160 at 5ft. I cant seem to lose and my hips are hitting the walls.... my question is this... a lot of people discuss, sets, reps..form...All this is greek to me... also the heart rate thing...something X's my age and check my pulse...Ive heard it _--- I have no clue what it is and once I check my pulse what am I looking for??? I am clueless and someone told me the other day if I am not monitoring my heart rate I could be wasting my time working out...... So please - in laymans terms... HELP!!!!

REPS = How many times you would do a curtain exercise motion without stopping

SETS = Would be the how many times you do one machine or exercise

For example if I did 15 bicep curls without stopping, and then did this once more, and then again. That would be 3 sets of 15 reps.

Does that make sense...now I don't know if I understand it after reading that...lol

and i will add for heart rate.....for fat burning i believe it is something like HR of 65% of max, and cardio/endurance is like 80%. hope that helps somewhat

UNDERSTAND?