Isn't it just beautiful? I think it's sometimes called Bal Kriya (but not too sure)

It's talking/describing Lord Rama as a baby.

Thumak Chalat Ramachandra, baajat painjaniya is litterally saying that as he walks the ankle bells around his feet chime (meaning metaphorically how sweet he is)

It's in Hindi, and very very popular. A fantastic rendition be lata mangeshkar can be found on her cd called Ram Ratan Dhan Payo

It suggests that it's been written by the saint Tulsidas (scriptor of the Ramayana)