hammer on

Guitarists do not always play a note by using a pick. There are instances where other techniques are used to play a single or series of notes on the guitar. The first technique we will look at will be a hammer-on. The concept of a hammer on is fairly simple - you begin a hammer-on by playing a single note anywhere on the guitar, then, WITHOUT picking the string again, you HAMMER-ON another finger on a higher fret of that same string. 
Take the above image as an example. You would use your pick to play the 5th fret of the B string (the 2nd string) and you would then hammer-on using a different finger with the same hand, on the 7th fret of the same string. Most commonly, you would be using your index finger (first finger) to fret the 5th fret in the above example, and whilst keeping it on the 5th fret while you pluck the string, you would then follow the note without using your pick, but by pressing your 2nd, 3rd or pinky finger (whichever is most comfortable to use) firmly onto the 7th fret of the same string. You should be pressing the tips of your fingers when hammering-on.