[Tykelad]

many people write " don't let them get too leggy"

What exactly does that mean ?

Don't laugh....i am new to all this !!

Tyke

[Ice]

It means they develop very long stems due to lack of light.

[plum crumble]

it means that you shouldn't let your new seedlings grow too quickly, so they become long, thin and fall over! It means they haven't put enough energy into the rooting system. Unlikely to result in strong healthy plants.
Don't worry about asking questions, we all had to start somewhere, and we never stop learning!