Some people may use the terms drunk and tipsy interchangeably without realizing that these are two completely different things. A tipsy person is someone who is affected by alcohol but still remembers the different things that may have occurred during the time when people have already started drinking. A lot of people who are just tipsy do not go through hangovers and can still function the day after like nothing happened.
Those who have gotten drunk have experienced something different. They may not remember the things that they have gone through and they would be nursing a hangover the day after. Their body may try to expel the alcohol from their body by vomiting while those who are merely tipsy will not see the need to vomit.
When someone says they are 'tipsy,' this generally means to say that they have had a drink or two and they have developed a nice, pleasant buzz. The person is just starting to feel the effects of alcohol, and they are having fun. The person still can walk and talk, and their judgment is still intact. When someone becomes drunk, they will generally slur their words, they may see double, or they may even sway or stumble from side to side. Sound judgment and driving skills are starting to become impaired at this point.
The person may also have an encounter with the opposite sex, which they may either regret the next day or not remember very well. Saying that someone is a drunk means that they are a habitual drinker, and it is having a negative impact on their life. They may be at the point that their drinking is affecting others, and they may need help.