How many orders do we get?

For clarification, I am coming from years of playing Guard in 40k but now I'm playing Astartes and in 40k I'm used to a limit on orders based on number of officers. Which is leading to confusion in LI. Do I have an order limit? Range? Can I give any unit any order(besides fall back)?

Thanks ahead of time me and my friend are the only ones at the lgs who play so were fumbling to success together!