There are 3 different presentations - Primarily Inattentive, Primarily Hyperactive/Impulsive, or combined presentation. We no longer use ‘ADD’ as a diagnosis - it is now referred and known as either ADHD, ADHD (Inattentive), or ADHD (Combined).
If you are 16 years and younger you need to meet 6 criteria out of 9 from the DSM-5 (The Diagnostic and Statistical Manual) to receive a diagnosis. The symptoms also need to be shown in more than one environment e.g school and work place or school and and in your social life.

Adults over 16 years old need to meet 5 out of 9 criteria to meet a diagnosis according to the DSM-5, and also have to have these symptoms be shown in more than one environment. 

The common experiences may vary - someone who is presenting with an inattentive presentation may have more trouble focusing on certain tasks, find themselves distracted easily, forgetting or misplacing items, tuning out of conversations, struggling with placing attention on the thing at hand like the conversation they’re in. 

Someone with a Hyperactive/Impulsive presentation may find themselves feeling restless, ‘feeling like they are driven by a motor’, talking excessively, un-intentionally talking over people in conversation, fidgeting and finding it hard to stay still. 

All presentations may experience things like ‘time blindness’ which is basically a difficulty in dedicating the correct amount of time to various tasks, either overestimating or underestimating time towards things. 

People with ADHD are also known to be very creative and able to think ‘outside the box’ more often!