Usually, a couple means two and a few means more than two (but not a large number) but That's not a hard rule and they are often used interchangeably. You can also say several times (Usually for a number of times more than a few). In other words...couple < few < several < many < all the time.

Couple=two A few = 2 to 10 about 4 to 6 usually but it depends on the speaker. Sometimes it leads to a little confusion between two speakers. If one refers to more than say 15.