The Eight of Pentacles (Eight of Rocks) is the apprenticeship card. This is the card that shows up when you are gaining new skills as well as experience in a career or job. This also is the card that shows tasks that you are doing that are repetitive since that is how you learn them and become a master in them.
if you are getting hands-on training for a career such as you are going to school to become a mechanic, for example, this is the card that fits it. That is because before you can become a mechanic, you would have to work in a co-op setting in a garage so you learn skills on the job. You would do this while you are still in school. This would involve you doing many repetitive tasks such as working on the same components in different cars that customers bring to the garage. And that means you are gaining the skills and the experience to become a mechanic. That is when mastery has come in. After all of that experience and practice, you have become a pro mechanic.
When the Eight of Pentacles shows up in reverse, it can be indicative of either learning skills on your own for your own purpose, or you are being a perfectionist and now allowing yourself to make mistakes. Remember, that is the only way to really learn. Or you are doing another activity that is misdirected.
Astrologically, this card is tied to the Sun in Virgo.