Not my specialism, I'm generalist HR, but have worked closely with them.
From what I've seen, you've got to love admin and data analysis.
When I was HR admin, our L&D admin had much more repetitive work. Book training, set up rooms, book catering, liaise with training suppliers, argue over invoices, liaise with trainees, print off training packs, collect feedback. It was much more straightforward admin/event organisation than HR, if you see what I mean.
At higher levels, they do a lot of data analysis to evaluate the effectiveness of training, and work with other departments to agree and develop training programmes appropriate to each department. Also involved in graduate schemes, apprenticeships, induction events, internal development schemes.
They are not often involved in delivering training themselves.
That's my experience. To me, it looks boring, but I'm sure people love it, but more admin/analysis/project management type work than HR side, so it's not for me.
As a generalist, I've always got involved with designing and delivering training more than them, if that's what interests you? Eg, where I am now our L&D team have agreed with directors a new programme of management training for new line managers. But it's back to us generalists to design the actual content and deliver it.