If you make an ignorant comment, your listeners might laugh at you, might get mad at you, or they might patiently instruct you in the ways that you are uninformed.
People can be generally ignorant, meaning that they are uneducated and lacking in sophistication. Or people can be ignorant of specific types of information. In fact, we all are. For example, most of us are ignorant of the particulars of nuclear physics and ignorant about what it takes to be an astronaut. Sometimes people are also labeled ignorant if they are rude, inconsiderate, or narrow-minded.