Lactated Ringer's, also known as Hartman's solution, LR, and Ringer's Lactate is an isotonic crystalloid solution that in both its composition and pH closely mimics the electrolyte concentrations found in the body’s extracellular fluid, making it an ideal way to replace lost fluids and restore electrolyte balance. It is generally considered safe and better tolerated with less risk of water retention compared to normal saline due to its significantly lower sodium content.