Elastic drive is a new special way of synchronization. When this option is enabled, files are not downloaded on your hard drive. You can view just a list of these files. They are downloaded only when you start working with these files (open, rename, etc.). Elastic drive option saves free space on your hard drive and makes synchronization faster.
How to enable synchronization
You need to have the latest version of Bitrix24Desktop app installed. Click the "cloud" button in Bitrix24 desktop app menu. Then click the cogwheel button > Settings. Specify Folder where you want your files to be saved and enable Elastic drive option in this section.