To add to Trigbomb's post,
CS is considered highly important as 1 champion kill (without bounty) is typically worth somewhere around 20-30 CS (depending on which creeps are killed). So even if you aren't killing your enemy, if you are farming CS better you are winning the lane.
Not all creeps are equal. Siege minions are worth more than melee, melee are worth more than range minions. All jungle minions start with relatively low gold worth, but they become extremely valuable around the middle of the game where the main minion in each camp can be worth 50+ gold.