(This might seem obvious to some but it has been asked, and it is 100% fine to ask! 👍 )

Hashtags are where you put a # in front of a word or phrase to indicate the topic you're posting about, which makes it easier for people to find your post. Lots of questions answered about hashtags here:

➡️ https://fedi.tips/what-are-hashtags-how-do-i-use-them-on-mastodon-and-the-fediverse

For hashtags with several words, put them together without spaces, with capital letters #LikeThisExample

You can follow hashtags too:

➡️ https://fedi.tips/how-do-i-follow-hashtags-on-mastodon-and-the-fediverse

#FediTips

What are Hashtags? How do I use them on Mastodon and the Fediverse? | Fedi.Tips – An Unofficial Guide to Mastodon and the Fediverse

An unofficial guide to using Mastodon and the Fediverse

p.s. After I posted this, thought of a million other questions that people have asked about hashtags, so I did an article about them at https://fedi.tips/what-are-hashtags-how-do-i-use-them-on-mastodon-and-the-fediverse and edited the link into the original post.
What are Hashtags? How do I use them on Mastodon and the Fediverse? | Fedi.Tips – An Unofficial Guide to Mastodon and the Fediverse

An unofficial guide to using Mastodon and the Fediverse