Excerpts are the short extract from your post. And WordPress always adds automatic excerpt when none is set, but this automatic excerpt is not always the solution. Sometimes we need to customize it according to our needs. Here is a simple step by step process on how you can customize your post excerpt.
Step 1. Log into the WordPress Administrator if you’re not already in it.
Step 2. Open your page or post (or create one if you’re starting new one).
Step 3. On the right side of the window, you should see the settings column. Click on the settings icon in the top right corner if you are not seeing the settings column.
Step 4. Next scroll down and find Excerpt. Click on the drop-down arrow to expand the option.
Step 5. Write your excerpt and save your post.