A curved line and the letter H indicates a hammer. The first note is played but the second note is produced by hammering on the left hand finger which plays the second note.
A curved line and the letter P indicates a pull-off. The first note is played but the second note is produced by pulling off the finger which is playing the first note.
The letter S and a straight line represents a slide. If the line comes from below the number, slide from a lower fret but if the line is above the number, slide from a higher fret. The third example on the right shows the desired fret to slide from.
The letter B and a curved line represents a bend. The note is played by the left hand finger which bends the string (from the note indicated in the tab).