Instagram allows you to better express yourself and tell others about the things you care about by using hashtags and profile links in your bio section that lead to their corresponding pages.
For instance, influencers and others may use such hashtags as #iPhonePhotography#cats#guitarlover#pencislsketching or #makeuptoturial to convey to other people what their account is all about, which topics they’re passionate about and so forth.

Using #hasthagts and @mentions in your Instagram bio

To mention someone’s profile in your bio, simply including a “@” and the app will turn it into a live link that leads to that person’s profile. 
When linking to a person’s profile in your bio, they’ll receive a notification and can remove the link to their profile to preserve their profile. In that case, their profile will remain on your your bio page but without a live link.
To edit your bio, open Instagram for iPhone and tap the Profile tab at the bottom, then tap Edit Profile at the top of the screen. After writing your bio with optional hashtags and profile links, tap Done to save the changes. Whether you type a “#” or “@,” Instagram will present you with a list of recommended hashtags and accounts in the typeahead.
As a reminder, you can write a bio of up to 150 characters on your profile. Anyone can see your bio, regardless of whether your profile is public or set to private.