Maple syrup is made my boiling maple sap, which is about 2% sugar. It takes about 40 gallons of sap to produce one gallon of syrup, which has a sugar concentration of about 67%. Maple sap contains mostly sucrose, but also nitrogen and minerals, carbohydrates and volatile flavor compounds. [x]

Trees move water through their vascular tissue: a system of tubes that runs through the plant, analogous to the veins in the human body. There are two types of these tubes, xylem and phloem. The xylem moves water up the plant, from the roots to the leaves, and the phloem moves sugar-rich water down to feed the body of the plant. When you wound a tree, the sap is liquid leaking from the vascular system. [x]

A sugar maple, Acer saccharum. 

Tree sap, which is actually phloem sap from the tree’s vascular system. Phloem tubes deliver nutrients produced in the tree’s leaves to the rest of the plant.
The damage to the tree trunk you see here was done by a woodpecker.
Photo by me.