Vines are fast-growing, light-loving spindly plants that specialize in growing up trees. Theirs is a different strategy to light gathering, and reach well-lit zones by efficiently dispersing seeds and then using tall plants to get enought light. They're a diverse group of many different kinds of plants and many are used by local people for handicrafts and native medicines. If sufficient vines enmesh a tree, they can bring it down if a nearby connected tree falls during high winds or heavy rain; such are the interconnections of the rainforest.
Trees growing at the margin of forest, such as at river edges or in forest gaps are especially prone to being colonized by vines. These aggressive plants rapidly grow up the trunk and allow easy access for animals such as monkeys. Important groups of vines include morning glory (Convolvulaceae) and passion flower (Passifloraceae).
This photo shows the high light conditions at river edges. The high level of light causes trees to be prone to colonization by fast-growing vines. You never see this deep within intact rainforest.