Eh. There are definitely jobs that you can grab random guys off the street for and they will be okay enough at them to get started right away or will be able to be trained to do them in an afternoon. Think of any time you’ve done a volunteering project - you don’t get any specialized training to do this type of work, but you can go ahead and get started with maybe like a short explanation of how it works. Sure you won’t be as good as a pro, but you could get up to speed quite quickly if it was all you were doing. These types of jobs are becoming less and less common as they get automated, but they do still exist. That is what is meant by “unskilled labor.” It’s not a dig at the people who do these types of jobs, but rather that you don’t need specialized training to do them.