Well, you (or the students) can write or type directly on the board, as well as moving things around (such as windows).
It’s great for when you want to show examples of how to do things, in say, Powerpoint or Excel. (Do you teach any of these programs to your kids? My mom does basic Powerpoint and Word lessons that the kids adore.)
If you’re doing math, you can put some problems in Notebook (I think that’s what it’s called) then have students come up and try to solve them. It’s a great warmup in the morning or before a worksheet.
I’m not sure what kind of reading/language teaching is done in 5th grade, so I can’t really comment on that. (Let me know, though, and I can give you some ideas.)
Science and social studies videos, images and diagrams can be shown on the smart board (so it’s sort of like a projector), with you or the students circling or drawing an arrow to important points.
What kind of objectives do you have in your classroom? For instance, my mom has to teach specific math objectives (double-digit addition), specific language objectives, etc.