No XEM in wallet?

Please excuse me guys. Im VERY new to crypto currency. I have a mac and downloaded nano wallet. I have bitcoins in COINBASE and used changelly to buy XEM with my BT and used the wallet code to transfer the XEM I bought into nano wallet. Does that sound about right? I waited 5 min and bingo, It was in there… Roughly $50usd worth of XEM. Its been a week. Today I tried logging in and noticed my nanowallet icon in my dock had a ? on it. Which means the program was missing… I re-downloaded it, logged in and now my wallet is empty. There is no “confirmed” XEM in there. Whats going on guys? And please talk to me like I know nothing. Im new and I don’t even know what a node is. Im just figuring all this out…
Thanks for your patience.

never mind… Just figured it out… I wasn’t on a NODE… It was red…

If a red circle is displayed in the mark of the node, it means that it can not communicate with the set node.
Please select a different node from the node menu so that a green circle is displayed.

In that state, will your balance be displayed?

thanks

Thanks. I figured it out… Btw, what exactly is a node?

The meaning of the node here means the server saving all the block chains of the current NEM.