Sorry Brother, and thanks. You caused me to do some looking into the difference.
I found this on a random google search. Kind of puts it into simple terms.
"As history unfolded, these [secular, or “diocesan”] priests lived out in the world with the people they were serving. The Latin word for “world” is “saeculum”, and there’s the derivation of the expression “secular priests”, those out in the world, ministering to God’s people. As the years passed, there were men and women who voluntarily decided to go apart from the world, taking the three vows of religion, namely, poverty, chastity and obedience.
Any man or woman who makes the three vows is called a religious—a religious priest, sister or brother. This essentially is what makes a “religious” different from a “secular”. The secular priests never take the three vows of religion. They do make a promise to their bishop at ordination to obey him as their spiritual leader for a particular diocese, and they also make a promise to remain celibate—not to marry. It bears repeating, to say that diocesan priests do not take the three vows of religion—poverty, chastity and obedience. The promise of celibacy is not the same as the vow of chastity."