What it means
SRT, or SubRip, is a text subtitle file. Each cue has a number, a start and end timestamp, and one or more lines of text. A blank line separates cues. The subtitle is a separate resource; it is not the video or its audio.
1
00:00:01,000 --> 00:00:03,500
Keep the original source.Here the caption starts at one second and ends at three and a half seconds. The final three digits are milliseconds, not video frames.
SRT versus a transcript
A transcript can contain the same words without display times. An SRT adds cue boundaries. Giving a paragraph an .srt filename does not create those boundaries, and converting an existing SRT does not check it against speech.
A practical check
Keep the original file. Open a copy in the SRT/VTT converter, choose the target format, and inspect the preview before downloading. Test the file beside the intended video. YouTube's supported-file guidance calls for basic, plain UTF-8 SRT; other players can differ in what they accept.
Common mistake
A valid timestamp is not evidence that the wording is right. Review names, numbers and timing against the recording. For overlapping or hard-to-read cues, use the reading-speed checker.