The term "trickle charger" refers to a battery charger that charges at a low amperage.
What is a trickle charger?
Many battery chargers provide different amperages, the idea is to charge a battery slowly or quickly depending on the need. Some are also designed to be left connected for long periods of time without overcharging. So when you hear people talk about trickle chargers, that is usually what they are talking about.
For general use, any battery charger or trickle charger that delivers between 1 and 3 amps will do. You really don't need one with trickle mode monitoring unless you want to leave the charger connected for some reason.
As for why you should charge your battery instead of driving around on it, there are two issues. First, the alternator can only supply a limited amount of amps, so the battery will likely still be nearly dead if you are only driving to work or running errands. The other issue is that alternators are not designed to charge completely dead batteries.
