If your video file is named something like MovieName.1080p.BluRay.x264 , look for a subtitle file with a similar "tag" (e.g., BluRay or WEB-DL ) to ensure the text lines up perfectly with the audio.
Likely what you're referring to. It lets you search for subtitles by filename or title and downloads them in .srt format, which works with almost any player. Sottotitoli - scarica i sottotitoli per film e ...
Always look for .srt files; they are the most compatible and easiest to edit if the timing is slightly off. If your video file is named something like MovieName