There are different rubs for everything we smoke or grill or barbecue. Brisket rub, chicken rub, pork rub, rib rub, fish seasoning, prime rib rub, roast rub, steak seasoning, general rubs, regional type rubs, etc, etc, etc. There are hundreds of variations for each item you want to cook.
If you want to barbecue something, just ask folks here what their favorite rub is for ribs, for example. You'll get several examples.
My recommendation is buy
Paul Kirk's Championship Sauces. In it, he explains basics for rubs, sauces, seasonings, marinades and such. For each, he offers several suggestions including what each rub or sauce can best be used on.
You can make your own or go down to your local grocery or barbecue store and find rubs already prepared. The label will tell you on what product the rub is best used. My pantry has over a dozen types ready for whatever I'm ready to barbecue.