Teresa

Yes it is confusing at first. As noted, Bolus just means filling the syringe & pushing it thru the PEG tube. An 8 oz can takes under 5 minutes. For me gravity meant using the feeding bag up on a pole that drips down into my PEG. An 8 oz can takes 35 minutes for me that way.
I see that Christine & Angelia refer to gravity as using the syringe instead of feeding bag to let "gravity" drip it into the PEG.
I have never used a Pump as the gravity system with a feeding bag on the pole is slow enough for me. I am working up to doing one Bolus feeding a day with the syringe but that sometimes upsets my stomach.
Finally, last but not least, what type of holiday would it without using the best (actually the only good part as far as I am concerned) part of having a PEG: using the syringe to bolus feed wine down it. Beer works but can be fizzy & upsetting. Wine is the right consistency plus the alcohol cleans out & sanitizes my Y extender tube and the PEG.