OK just going to include the highlights:
Thee are stimulant and non stimulant options.
Stimulants tend to stay in the body for a short space of time. Most non stimulants you have to take over a period of time and build up in the body.
Stimulants are basically a safe form of speed (I am massively over simplifying here for brevity... I am not a doctor but my kid has been on ADHD meds for years). The idea is that kids with ADHD are actually missing some stimulant in their body so their bodies overcompensate by making them act really hyper. You plug the 'gap' with a stimulant and the child calms down. Many of these medications if a non ADHD person takes them, will get high, not feel calmer.
Side effects of stimulants can be difficulties, sleeping, loss of appetite, in some cases anger or agitation.
Medications vary by their release mechanism. Some release through the course of a 12 hour period slowly, others release immediately and others a combination.
Brands include equasym, ritalin, medikinet.
If your child is diagnosed adhd they will likely be offered equasym as a first line to try. The good thing is if your child hates it, it's not addictive and doesn't build up int he body so you just stop taking it and back to square one.
Non stimulants vary a lot more, and are basically every other drug that can be used to treat adhd that isn't a stimulant. These include tranquilisers, anti deressants, anti anxiety meds.
Common ones I know of are guanfacine and atomoxetine.
Usually your doc would want you to try a stimulant first as these are easier to monitor and you can stop immediately. Non stimulants tend to take a long time to build up, and some take a long time to withdraw from.
There are as many side effects as there are medications in non stimulants. Every med will have its own side effects.
As the poster above said, different children respond really differently to different meds so I'd be wary of reading into others' experiences as your child will respond in their own way. For our part, my son tried every single stimulant and a few non stimulants before stabilising on atomoxetine.