FediTips , 
As well as replies, are three ways to interact with a post on Mastodon:
⭐ Favouriting - This lets the post's creator know you enjoyed their post. It's the equivalent of a like.
🔁 Boosting - This shares the post with everyone who follows you, and adds the post to your profile's timeline. It's the equivalent of a re-tweet.
🔖 Bookmarks - This adds the post to your private bookmarks list, without telling anyone you've done this.
More info including how to browse them:
➡️ https://fedi.tips/how-do-i-do-likes-and-re-tweets-in-mastodon-and-what-are-bookmarks/