Bowing On And Off The String
Notes that are indicated to be played separately can be played on the string or can allow the bow to bounce off the string. With a large body of string players, all playing repeated quavers together, for instance, in the accompaniment of a piece by Haydn, Mozart or Beethoven, the effect of on the string versus off the string can be very different.
Bouncing off the string has more resonance and is probably easier for most orchestras to get together. Playing on the string is, on the contrary, more forceful, but is harder work and also harder to get together.
The same differences apply to notes that are not repeated but move conjunctly - you can hear for yourself the difference of the power and force of the first example above, in comparison to the slightly more 'fairy-like' quality of the second.