There are two fundamental strokes you use as a pick player. One is down-picking where the pick's direction is towards the floor and the other is up-picking where the pick moves upwards, towards your face. Both are vital, sharing the work required to sound the strings.
At a very fundamental level, many guitarists use down-picks on down beats and up-picks on up beats. This allows for technical consistency that keeps general playing simple. You'll see this throughout the examples below.
