What do certain cat noises mean?

There was a baby kitten making tiny, loud 'meows' outside my house. I wanted to go out and see if it was okay, and maybe put it in our garage for safety, but my parents wouldn't let me. It's right outside my window and now it's making quieter meowing noises that sometimes end in screeching sounds. Like the kitten may be halfway hissing but also meowing. Or he/she could be sick. What do the noises mean? Should I try to get him help tomorrow?