Ok now i am a bit wiser, yes mains to low voltage AC / DC adapter, there ok for fixed voltages, some only put out one voltage, others have a selector switch, say from 3, 4.5, 6, 9, 12 volts.
As a rule the current drops off as the voltage increases, so say the units 1200 milliamp, some units will give this power level at max voltage, other units wont, for instance another unit might give you 1000 milliamps up to 9 volts, but at 12 volts say 800 milliamps, it pays to read the ratings for max power for given voltages across the whole range.
Yes these units if regulated can power your projects, build a small DC connection box with a DC socket in it in one side and drill some holes and add posts or sockets for 4mm plugs and crocodile clips, add a fuse and switch if you want, a latching switch and a momentary switch for short power bursts is useful.
It very much depends on projects you build, they will work fine for a lot of projects, try and get a good quality one with the voltages above, this gives more options powering circuits, you can always upgrade later, a picture of a box i am on about, this one is fixed for radio use, but you can select what voltage you want for a given project.
Dave.
Add as many switches as sockets or binding posts, sorry poor pictures, only had a phone camera to hand, but a box like this can allow multiple voltages either by multiple pole switches, or posts / sockets.