Depending on the blog layout you choose, some will use excerpts for the post summary by default. Others will give you the option to use regular content where you can insert your More Tag (read more).
Alurra gives you the option, again, depends on the blog layout, to choose if you want excerpts.
Excerpts are basically a set number of words to show for your post summaries, which helps keep a consistent look to your blog. Excerpts also allow you to create a custom introduction to your full post without using part of your actual post.

NOTE: When using excerpts, all formatting and media will be stripped out until you view the full post.
- Go to Appearance > Customize > Blog Options
- Look for the Blog Excerpts setting and click on the toggle to enabled (turns blue).
- You can also use the Excerpt Length slider to adjust how many words to set.
- Click the Publish button.