When Lightning Communities were first introduced back in October 2015, there was only one theme available, Napili. This was great because it was a simple responsive theme with a few customisable options.

Since then, customers have asked for more features and Salesforce has delivered these, such as custom branding, but until recently there was still only on Lightning based theme available.

With Summer 18, Salesforce have introduced 4 more themes to the palette. This gives customers more options and configurable areas than ever before.