When someone says they went backpacking they could be referring to one of two different activities. Although they are similar in their drive for adventure they are quite different in essence. Backpacking as it is commonly used in the United States refers to hiking long distances and spending the night in the wilderness. This form of travel is characterized by walking long distances, sleeping in a tent, and carrying all necessary gear to do so on your back. Even within this type of backpacking there are further sub genres like ultralite, which reduces pack weight at all costs, mountaineering, which includes backpacking through mountainous areas requiring the use of ropes and climbing equipment, bushwhacking, which is basically backpacking off trail requiring route finding, and thru-hiking, which is backpacking very long distances like the famous Appalachian Trail. These various forms are all considered backpacking because they all have those same basic elements, carrying gear on your backing, hiking and sleeping in the wilderness.
The second meaning backpacking adheres to is more commonly found abroad. I found this definition used most frequently in Central America and in Europe. This term refers to traveling with a backpack, instead of a suitcase. Although this form of traveling is also closely associated with budget travel, and sometimes more with younger populations, staying in traveler hostels instead of hotels. The backpack is used to carry all belongings for the duration of the trip.
When I travel abroad I tend to combine the two into a hybrid form of backpacking. I use a backpack to cary all my belongs but I also bring along the things that allow me to explore further into the wilderness like a stove, a tent and a sleeping bag. I am in no way trying to say one way is better than the other I am just pointing out the difference. I love both equally and this blog is dedicated to both forms. You should try them out for yourself!