Once you've got your categories narrowed down, then you can start getting into the nitty-gritty differences between strings. For instance, electric guitars will give you the choice between nickel (for authentic vintage sound) and stainless steel (for maximum durability). Some string manufacturers have exotic material options with their own unique characteristics, like Ernie Ball's Slinky Cobalt strings. With so many subtle differences separating guitar strings, you owe it to yourself to browse carefully and look at all the choices on the table before making a decision.
Unlike many string instruments which use a bow to create a sound, guitars are played by plucking or strumming the strings on the instrument, which vibrate to create a sound. Chords are played when the guitarist holds their fingers down on more than one individual string to change its length, which in turn changes the frequency of the vibration created - in other words, it creates a different note. Performers often use guitar tabs, rather than sheet music, when learning music: this acts as a kind of 'map' to teach guitarists where to put their fingers on the strings.