Some people may consider a growl and/or a snap as aggression. Others would say it is not aggression until the dog bites. Whatever your definition, if your dog's behaviour is a problem to you then it is a problem that needs resolving.
Firstly, it's important to understand the true meaning of the word 'Aggressive'.
It means 'to feel hostile'. Note the word 'feel'. There is a distinct difference between a dog feeling aggressive and a dog exhibiting aggression.
Many dogs exhibit what is interpreted as aggression, but they may not be feeling aggressive. Displays of aggression are usually a survival strategy for dogs who find themselves in a situation they cannot cope with.
As an example, a dog may be barking, snarling, lunging and in some cases, even make contact with the other dog/person. But in this moment, they may not be feeling hostile towards them.
You need to understand and focus on the motivation and intention of the behaviour, rather than the behaviour itself. Most dogs who exhibit aggression are fearful There are some dogs who are aggressive, but they are few and far between.