They mean it in a good manner. They're attempting to convince you that you possess attributes associated with a nice guy, and that someone would be fortunate to date you. It's meant as a complement. Just bear in mind that what some women consider a "catch" is not always what other women consider. One woman may love a "catch," while another doesn't care for them at all. The term "catch" came from fishing. When you "catch" a fish, you bring it into shore alive so that you can enjoy its company for a while before killing it. The same goes for men who are looking for love. They want someone to enjoy while they continue on living their lives. Some women like men who are strong and capable enough to take care of them, while others prefer men who are more sensitive and compassionate. What matters is that each man decide for himself what he wants in a partner. In modern day usage, the word "catch" means a very attractive or charming person. This phrase comes from fishing where they would "catch" big fish by using small hooks. So, when you hear this term being used among friends, remember that it means you'll be enjoying yourself while you wait for someone special to come along. There are many different types of catches. There's the bad-boy catch, the crazy catch, the dark-horse catch, and even the plain old catch.