Float is a generic name and a stage of charging characterized by low amps at 13.2-13. Volts...to keep a battery topped up at 100% charge. Sometimes known as a trickle charger as well.
Maintainers often include some other circutry to "read" the battery state and turn off and on accordingly, they may also include a "pulse" function (which is totally worthless).
I've pointed out many times before that a fully charged battery
with the negative post wire removed
will hold its' charge in the COLDEST weather for at least 90 days...and likely much more and that most float or maintenance charging is unnecessary and just one more thing that can go wrong.
In the context of THIS thread I'd point out that chargers of house batteries which do NOT also charge the engine battery can be permanently compensated for by adding an ECHO charger. This simple device hooks to the positive terminal on the house bank and then to the starter batt. Once the house bank reaches 13.0V (from the charger or alternator) then it spills over to charge the engine batt & turn off when that is fulll. Cost about $100.
There's also a cheaper alternative called Trik l Start that works in a similar manner which I have no experience with & goes for about 50 bucks.
Ultra TRIK-L-START Starting Battery Charger/Maintainer
Note that both these systems rely on a fully charge house bank and so don't do you much good if the main batts are not plugged in...but can be the solution to keeping the engine batt topped up when you sit in a park for a long time with ongoing parasitic drains as is common.