The Fluid Grid is a machine added by Refined Storage. It is a point of access in the Refined Storage digital storage network specifically dealing with Fluids. Fluids can be added via Buckets, External Storage, or Importers. Fluid Storage Disks or Blocks are required to store liquids unless external storage is available.
The interface of the Fluid Grid is similar to normal items however the liquid is displayed in buckets. If Buckets are in the storage system you clicking the liquid will fill a bucket and move it into the player's inventory. Exporters can be used to send fluids directly to machines or storage tanks.