The "U" or "K" symbol on a product means that it is certified kosher. Kosher means that the item was prepared in accordance with kashrut, Jewish dietary laws, under the supervision and approval of a certifying organization and rabbi.
It does not indicate that the food is vegan, as animal products may also be labeled as kosher. "Kosher parve" denotes that the food is deemed "neutral," which means that it does not contain meat or dairy products. Nevertheless, kashrut does not interpret "meat" in the same way that vegans do. For instance, fish and eggs are considered parve, so prepared foods marked as "kosher parve" may contain either of these as ingredients.
A "D" means that the food is designated "kosher dairy." That is, it is certified kosher but contains dairy products or derivatives and, in accordance with kashrut, is not permitted to be eaten with meat. "DE" signifies that the food does not contain dairy products directly but was prepared on equipment that also is used to make foods containing dairy. In terms of kashrut, these foods are considered "kosher dairy," even though the equipment is thoroughly cleaned before each run and the product itself is dairy-free.
A kosher symbol on food does not imply that that the food is vegan. Kosher certification merely ensures compliance with ritual animal slaughter and certifies that meat and dairy products have not intermingled during processing. There is no direct correlation between kosher foods and veganism.