SSRIs are a type of antidepressant, the name stands for Selective serotonin reuptake inhibitor. They are often successfully used to treat OCD, PMDD, anxiety, PTSD and depression.
Dopamine is a neurotransmitter involved in many different functions, including movement, motivation, reward, and pleasure. It is one of the most important neurotransmitters you have to get to know if you want to understand ADHD better.