Question too broad and there are lots of variations in the Scandinavian Defense (example Black can play 1.e4 d5 2.exd5 Qxd5 but also 1.e4 d5 2.exd5 Nf6).
As Black :
Imo the Scandinavian player is often first a Caro–Kann player but as he can't like 1) e4 c6 2) d4 d5 3) exd5 exd5 then 4) c4 or 4) c3 (Carlsbad Pawn Structure), he will play 1) e4 c6 2) d4 d5 3) exd5 Qxd5 4) Nc3 Qa5 then he will limit himself to the Scandinavian Defense (because he will only have one opening to know)
White very often want to play the o-o-o vs o-o strategy which makes the opening much easier to study and otherwise probably the most annoying variation (even if doubtful) is 1) e4 d5 2) exd5 Qxd5 3) Nc3 Qa5 4) b4
What is your experience playing the scandinavian defense?