Full bolt ons are your basic mods: cold air intakes, full exhaust, under drive pulleys, tunes, etc..
Typically intakes, nitrous
, cams, supercharger and SC pulleys, etc.. are not considered "bolt ons" even though they technically are.
As GrabberMeBlue said, things you can do without getting into the engine.
The term can also vary by car.
Like my Z28, people ask and I say it's full bolt ons and H/C/I with spray. Meaning all the basic mods plus different heads, cam and intake.
On my Talon, bolt ons typically are full exhaust, intake and boost controller.