Tangoes are mostly seen during the early game laning phases as on-the-fly regeneration items. They are similar to the Healing Salve in that they regenerate health, but do so at a slower rate. A major benefit over salves is that a Tango comes with multiple charges, and can therefore be used before the user drops to dangerously low levels of health. Another advantage is that the Tango's effect does not stop if damage is taken. This can allow heroes to continue farming against enemy harassment while regenerating health. This also means that a Tango can be consumed when being attacked during ganks and skirmishes to stay alive. Tangos can also be used to remove trees to facilitate escape or chase.
Tangoes may be used during the act of "juking" enemy heroes while running away. Many forest areas on the map have pathways that you can 'eat' your way out of or in to avoid or confuse an enemy chasing you.
The Tango has an additional use in games involving a Nature's Prophet on the opposing side. The item can be used to mitigate Nature's Prophet's Sprout spell, which creates a ring of trees around a target. By eating one or more of the trees with a Tango the target can easily escape the ring. Quelling Blade, an item which also destroys a tree, can be used in a similar fashion.
This item is recommended for nearly all heroes during the early game. The ability to heal during combat early on is essential to surviving the laning phase.
WC3 DotA Version