If you scroll through the description of an official music video, you will sometimes find the full lyrics printed under the credits. Not every uploader does this, but some do, and the text is often in the original language of the song. Occasionally the same description carries the lyrics in more than one language, one block after another. Because the uploader wrote or approved that section, it is their own official text. That is the main reason it is worth knowing about: it is the place where the words come straight from the people who released the video.
That origin makes it more reliable than the transcriptions fans post on lyric sites and in comment threads. A fan who listens and types is doing honest work, but mishearing is easy, and small mistakes get copied from page to page until they look like fact. When the uploader prints the lyrics, you are reading what the release team supplied. It is still worth treating it as a reference rather than a recording, because lyrics in a description can differ slightly from what is actually sung, and line breaks or spelling may vary between versions of the same text.
It also helps to keep the sections of a description apart. The credit lines above the lyrics tell you who made the song. A line that begins with something like "Lyrics by" names the person who wrote the words, which is a different thing from the lyrics themselves. Some descriptions print only the credits and no lyrics at all, and some uploaders add the lyrics later, so a description that looks bare on release day may change. If you are looking for translations, remember that a fan translation is an interpretation of the words, not official text, unless the uploader posts a translation in the description themselves.
One more thing worth knowing: lyrics are protected by copyright, and printing them on the official post is not the same as copying the full text somewhere else. This is why news sites like ours do not quote lyrics, and it is a good habit for fan pages too. This is not legal advice, only a plain explanation of how we handle it. If there is a line you love and want to share, link the official post and tell people where to look. That keeps the words with the people who published them, and it sends your friends to the most reliable version.