Slides and bends are among the basic guitar techniques. If you didn't hear about them before, you can check out Wikipedia articles: slides, bends.
Among well-known examples of using these techniques are: All Along The Watch Tower (Jimi Hendrix), Wanted Dead Or Alive (Bon Jovi), My Favourite Game (The Cardigans) and much much more.
With slides and bends support most of the songs on Songsterr will sound more realistic, and everybody will be able to see, hear and try to repeat these effects by themselves. Enjoy!