One of my three teaching jobs is at a free online public school for middle and high school kids. For many kids, this is a great opportunity. Homeschooling usually costs money. My school is free, and also provides students with a laptop computer and internet access. There are no materials to buy, and the curriculum is self-contained on the school's web site. Real, credentialed teachers are assigned to every student, and the student has a teacher credentialed in each subject. I have mostly taught English. This is very good for kids that need to stay home or need flexibility for whatever reason. The disadvantages are to their health. They spend hours at a computer and they do not always get the social contact they need. The same goes for their teachers.
If you are looking for programs that provide education on-line for free, be very careful. Not only is it doubtful that there are free training programs on-line, many of the on-line educational programs are "for profit". This means you would end up spending significantly more for an on-line course of study than you would for a university degree.
I am not sure if you are asking about free online resources to enhance education or if you are talking about actually participating in a program that enables you to get your education. I am not aware of any thing like that that is free.
These resources are also a boon to people who live in remote areas where purchasing educational materials would involve a long trip to a more populated area. For those who cannot afford to make such a trip as well as for those who are physically unable to leave their homes, the online educational resources make learning possible when it would not be otherwise.
Free online educational resources are very important, especially for people whose schools or families do not have the funds to buy educational materials.
For example, there are many sites with the full text of Shakespeare's works free online. These sites allow people to use these texts even if they cannot afford to buy them. By making resources available to those who cannot buy them, these sites are performing an important service.
If you are willing to learn more and to improve your skills without paying any cost and if you have knowledge in using the computer and you are capable to browse internet, free online education is the answer.
The online information is provided in various ways: video tutorials, free ebooks, free online tutorials etc.
If you want to get a diploma and you are choosing online education, you have to check if the online programs chosen are authorized, accredited and spam free.