I got some salsa from Smith's and it had a K in a circle.
Found it --- apparently means Kosher. But, Kosher salsa?
If it just has the letter "K" with no other distinguishing mark, it means that the maker thinks it's kosher but can't prove it. "K" is just a letter of the alphabet. The stylized K in the O is the mark of a particular certifying organization, Organized Kashrut, which means it's certified kosher according to the standards of that company, and its rabbis. OK is one of the oldest commercial marks. OU (Orthodox Union--the U inside the O) is the most widely accepted.
And, yes, kosher salsa. Vegetables have to be inspected, too, and kept separate, and there are more stringent cleanliness rules for knives that are used with "hot" or acid veg, like onions, tomatoes and peppers. There are additional food handling requirements, as well, and issues with the vinegar. It's actually harder to make salsa picante kosher than many other kinds of foods.
Additionally, one rabbinate is more particular about the handling of vegetable oil, for example, while another has a different interpretation, so while some people are fine with any hechsher (rabbinic mark), others will only take OU or a list of these yes, those no. Food handling equipment, such as plastic bags and gloves, can also be certified. OTOH, when an appliance which isn't itself a food vessel says it's kosher certified, that means that that organization's rabbi has supervised the Sabbath mode, which makes using it compliant with Orthodox Sabbath restrictions (e.g., the light doesn't turn on and off when you open and shut the door, and the appliance won't turn itself off, which many ovens and cooktops do nowadays after being on for four hours) and it's not about the food at all.
More than you wanted to know, huh?
Thanks. I assumed it could be complicated but never paid any attention. Interesting.