It's a tiny, self watering planter with water level indicator.
Water reservoir is in the bottom. A small string transfers the water to the soil.

Needed parts:

• water indicator (used Leni Wasserstandsanzeiger 7 cm GTIN 4004256260214)
• 2,5 mm - 3 mm string, ~ 6 cm long
• optional: soil like lechuza pon or expanded clay

Water indicator is obtainable via web, or in typical german hardware stores (toom, obi) and costs about 2 €.
It probably would not be too hard to design one by your own.