Online guitar lessons offer us a way to explore the near endless expanse of information without just meeting with a teacher once a week. How we use what we find online is as important as what we find.
Online instruction can replace meeting with a coach in person or compliment it. All of this depends on what type of learners we are. Ultimately, everyone we come into contact with teaches us something. When we go to jam with others, our open mind allows new levels of understanding to evolve.
Yet, formally meeting with a guitar coach ensures that a qualified person is evaluating and guiding our process. A lot goes into this relationship, and many of those factors also govern if we formally study with someone online, or just grab information from any online resource that we locate [how things typically unfold online].
If we are seeking study in specific styles [Classic, Jazz, Rock, Blues, etc.], there are countless resources and institutions which provide education in all of them. JamPlay and Jamorama are good starting points.