"Um" is a common filler word used in spoken language. It often indicates hesitation or a pause while the speaker thinks about what to say next. People use "um" to give themselves time to formulate their thoughts without losing the attention of their audience. In many cultures, using "um" is considered a natural part of conversation. It can help convey uncertainty or a need for more time to respond. However, excessive use of "um" may distract listeners and affect the speaker's credibility, making it important to be mindful of its frequency in communication.