Vim

Vim is the life force of the Toad species. When extracted from Toads, Vim resembles a green liquid with transparent images of sad Toad spirits; the Toad itself withers away and dies without its vim.

It is unknown if vim is unique to Toads, or if other fungal species such as Goombas or Amanitas possess vim as well. Considering the fact that "vim" merely refers to a Toad's life force, it is even possible that non-fungal species of the Mushroom World contain vim in addition to their life-giving fluids, such as blood. Vim has only ever been referred to in Mario & Luigi: Partners in Time, where a species of alien fungi known as the Shroobs harvested the vim from the Toads to convert into fuel. They did not target any other species, so this could indicate only the Toads possess vim, or at least the only type of vim that is usable by the Shroobs, which may or may not have vim flowing in their own bodies.

Mario & Luigi: Partners in Time
In Mario & Luigi: Partners in Time, the extraterrestrial Shroobs conquered the Mushroom Kingdom of the past, and abducted many Toads so that their vim could be extracted and converted into fuel for their flying saucers.

Captured Toads were taken to the Toadwood Forest and attached to special bio-engineered trees. These trees could actually suck the vim out of Toads, slowly killing the mushroom people. A Toad drained of vim would die and be discarded so that another Toad's vim could be drained. The vim would then travel through the roots of the trees to the Vim Factory located in the middle of the forest. A giant tree sat in the middle of the factory, absorbing the vim and sending the solution through pipes that led to the lair of Swiggler, a bio-mechanical Wiggler that had the ability to convert vim into fuel for Shroob Saucers with special chemicals contained within its body. Flying saucers would attach to Swiggler, which would then transfer the fuel into the ships.

Mario, Luigi, Baby Mario and Baby Luigi put an end to the operation by destroying the Shroobs, the giant vim-sucking tree, and the Swiggler inside the Vim Factory. It was eventually discovered that baby tears reverted the damage done by the Shroobs, and since at least one of the vim-sucked Toads, Toadiko, was later seen alive and healthy, it is assumed that the tears restored the life force to all the victimized Toads.