Transient options are builtin WordPress cache system, which helps speeding up your website. It basically stores the requested data of WordPress database for a limited time period so it can be used when a web visitor requests the same data within that cached time period. In few words this helps with the site’s cache.

Can I delete transient options?
Yes, you can delete Transient options and this will not affect your database.

What happens if I delete them?
WordPress will rebuild the cache of transient options afterwards.

Tip: If you are taking backup of your database or getting it ready to be moved to a new domain or host, deleting the transient options will reduce the size of your Database!