Lemmy doesn't have follow functions for users, only for the community actors. Lemmy users can't follow individual accounts. Though threads users can follow them, and also follow communities just like Mastodon users can. Also they can post to communities and reply to posts and comments in them the same as Mastodon users can.
(how to post to Lemmy from Federated Microblogs)
Title Section
Post body
Hashtags (optional, can also be in body)
Community Actor handle mention i.e. @community@reddthat.com
In a lot of ways it is better, supports hashtags, has full activitypub support (not just the group support) which allows following users, and allows boosting.
Though it also has severe drawbacks like a lack of MD support (glitch-soc has it but normal Mastodon doesn't), doesn't allow arbitrary link attachments like lemmy, and does not have good community/group view or threaded comments, though these last two are mainly front-end issues.