In Windows Explorer/Finder, there are two options for keeping your folder/files locally stored.
"Download folder" and "Start/stop synchronization".
"Download folder" downloads all files in a folder just once.
This makes the files available for offline use.
"Start/stop synchronization" downloads all files as well. The difference is that it also keeps your folders/files synchronized (eg.: always downloads remote changes, and uploads local changes as they happen) when it is turned on.
Start/Stop Synchronization can be enabled on a Share as well, this will keep all folders/files available for offline usage.