Sour diesel, tobasco, ammonia, metallic, coffee, sour milk, sweet lemon, black pepper, blueberry - these are all smells and flavors that are now infused into cannabis products and what you may smell when you're walking down the street, in your home, etc. Some cannabis products can even smell sewer-like, or they may be odorless. It can be helpful to get familiar with some of the terpenes to help you recognize cannabis in your environment.
Most concerning to non-users is that terpenes make the body more permeable so that cannabis can more easily be absorbed and affect the body. An article on terpenes from Green CultureED states, "that means these terpenes can influence neurotransmitters in our brain which entails that different strains may have different effects on our mood."
The articles below contain more information on what terpenes are and how they work.