Minimising Blogs

Hello
I have a number of blogs that the posts on the front page are minimised and you have to click on a button to the read full post. Good feature.

The blog I am setting up at the moment I cannot seem to make this happen. I have been going thru all the settings comparing all of the settings to see if there is something that I have missed.

Is this a feature tht I can turn on or off – or is there a plugin that makes this happen.

Thank you for any help in advance.