Yes, BBQ is very, very different from grilling or a cookout.
Grilling is what we do on the grill - hamburgers, hot dogs, chicken, fish, vegetables, etc.
BBQ refers to a style of meat that is slow-cooked & often smoked w/ some kind of dry rub and/or sauce.
A cookout is usually a gathering of people - more than just your immediate family. We‘ll either host or attend a cookout where there will be food grilling. There might also be some BBQ & other smoked meats at a cookout.
In our house, over the weekend, on Friday, we grilled hot dogs & brats, &, on Saturday, we grilled chicken breasts. Last night, we grilled hamburgers.
But, today, we’re smoking a pork butt & ribs in the smoker all day long for pulled pork BBQ sandwiches for dinner tonight. (We’re grilling corn to go w/ the BBQ sandwiches.)
And there are southern regional differences to BBQ - St. Louis, Memphis, Carolina, Alabama, Texas… In my area, BBQ is most often pulled meat (pork, beef, or chicken) or something like ribs or brisket w/ a tangy, tomato-based BBQ sauce.