The internet has become an integral part of all aspects of the music industry and can be an extremely useful tool for absorbing and gaining information at a very small price (and often free). With regards to accessing information to help with learning the guitar and music theory it is worth advising that you should apply a certain degree of scepticism when approaching certain sites. The fact that there is such a wealth of information on the internet often provided for free, the quality of these sites can often be poor. This is due to many reasons but as it is so easy to create a website and host it at low cost these days, this can have a detrimental effect on the academic and factual correctness of the information that is being provided.  This is precisely why 1 to 1 or group tuition for any instrument is vital due to the professional and academic backgrounds of the majority of teachers.