A fledgling is a fuzzy baby bird just learning to fly, or someone (like a baby bird) who's brand new at doing something. Awww.
If you're not talking about a baby bird, fledgling is often used as an adjective describing a new participant in something, like a fledgling senator still learning the ropes of how to legislate, or a fledgling drama program trying to build audiences for its plays. It can also mean inexperienced and young, like the fledgling photographer for the school paper who accidentally erases all the pictures. If you're British, spell it fledgeling if you like, both spellings are correct.