The following tutorial will help to explain to you the basic concept of reading guitar tab. Although it may seem complex, learning to read tab is quite simple, and you should find yourself reading tab easily in no time.
Guitarists are a unique breed. Chances are, if you play guitar, you are either self-taught, or have taken a small number of lessons via a friend or guitar teacher. If you were a pianist, however, you would have learned the instrument through years of private study, which would include both music theory lessons, and heavy focus on sight reading.
Nothing wrong with taking the more informal approach to learning music, but it does create some inherent problems when it comes to laborious duties like learning to read music. Learning to sight read takes a reasonable amount of work, without immediate benefit, and it is these sort of skills that self-taught musicians tend to avoid.
It's never too late to learn to read music... if you want to get serious about a career in the music industry, it really is essential. However, guitarists have created their own method of music notation, guitar tablature which, while admittedly flawed, provides a simple and easy to read way of sharing music with other guitarists.