Bitrate is the amount of data used to represent video or audio over a given amount of time, usually measured in megabits per second (Mbps). Higher bitrate generally means the file has more information to work with, which can translate to cleaner detail, fewer compression artifacts, and better handling of fast motion or complex textures. Lower bitrate means the encoder has to throw away more information, which can show up as blockiness, smearing, banding in gradients, or muddy fine detail. Bitrate is not the only factor in quality, but it is a useful signal when you are comparing similar formats and encodes.
A simple example is streaming versus disc. Streaming services often use lower bitrates so content can play smoothly over typical home internet connections, while UHD Blu-rays usually allow much higher bitrates because the data is coming from a disc, not a bandwidth-limited stream. That is why a streamed 4K movie can sometimes look softer or more artifact-prone than a 1080p Blu-ray, especially in dark scenes or heavy action. Also, codec matters. A more efficient codec like HEVC (H.265) can look better than an older codec like AVC (H.264) at the same bitrate, because it compresses more intelligently. So bitrate is best understood as one piece of the puzzle alongside resolution, codec, encode quality, and the source master.
