たり indicates actions or states that alternate
たり is a particle that connects to the ends of verbs, adjectives, and adjectival verbs, and is used to enumerate multiple actions or states or to indicate a range of actions or states.
たり is always used in the form of "〜たり, 〜たりする" or "〜たり, 〜たりした" with する or した always at the end of the sentence.
Japanese
週末には山に登ったり、海で泳いだりしています。
English
I climb mountains and swim in the sea on weekends.
Japanese
子供の時はよく遊んだり、泣いたり、笑ったりした。
English
When I was a child, I often played, cried, and laughed.