This is a kind of jumping spider, and it's only about 5mm in size. The males have a colorful pattern on flaps that extend from their abdomen during breeding/mating. In addition to this, they raise their back pair of legs and dance from side to side to win over their plain brown females.
Only found in Australia, they were classified as species Maratus volans because people originally thought the flap was for gliding after jumping. Wiki
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