A yukata: a lightweight cotton kimono worn in summer or as a bathrobe; often worn at festivals, hot springs, or as casual indoor wear.
夏祭りには浴衣を着て行くつもりだ。
I'm planning to go to the summer festival wearing a yukata.
旅館で浴衣に着替えて温泉に入った。
I changed into a yukata at the ryokan and went to the hot spring.
浴衣は普段着よりも簡単に着られる物もある。
Some yukata are easier to put on than regular kimono.