At the German Bahn website, sometimes in the comments in says "Bicycles conveyed - subject to reservation" Does that mean you may need a reservation only if you have a bicycle, or that you may need a reservation whether or not you have a bicycle?
You're covering one of the most difficult issues with German rail. "Bicyles conveyed" means there is a special carriage available on that train to carry biycles. Unfortunately prices for the transportation vary depending on who's actually running the train. All trains may look like DB German Rail and can be booked thru the bahn.de site, but especially the local and regional trains are operated by other companies, communities etc. Generally speaking you can bring your bike and if there is enough space you can take it with you and pay on board. That's also the easiest way. However, if for whatever reason there is no space left for bikes you wouldn't be able to take it on board - which rarely, rarely happens. When are you planning on traveling with your bicyles and from where to where?
Andreas - Thanks. We are not bringing bikes - I just wanted to know if the "make reservations" only applied to those with bikes.
I should have mentioned that we have Eurail passes, so that is why I ask if we also need a seat reservation on those trains.
"Bicycles conveyed - subject to reservation" means that if you want to bring a bicycle, you need a reservation for the bicycle. (This is common on IC trains due to limited space.) You do not need a reservation for yourself. In fact, virtually no German trains require reservations. (The exceptions are the 3(?) Sprinter trains.) If they do, they are marked with a white "R" in a red circle. (Search for Frankfurt to Munich on a weekday morning and the 7:14 should come up.)