Title tag display the page title at your browser, it also helps browser to bookmark easier when user add it into their favorite.
For SEO(Search Engine Optimization), title will be display at search engine result as a basic description about what actually inside your page.
That's why title tag become so important as the first impression for people get connect to your site.
When you install a blogger default template, every page that display at your site are totally bad practice SEO in title tag.
Here i try to show you an example default blogger title tag shown at Google SERP.
Now, you need to tune a simple code to let it look more better and clearer in Search engine.
Tune Title Tag For Your New Blogger BlogsStep1: Login into your blog and at the dashboard you click on the drop down menu to choose Template.
Step 4: Find the code where around 15 lines from the top.
Replace it with...
<b:if cond='data:blog.pageType == "index"'>
<title><data:blog.pageName/> | <data:blog.title/></title>
Step 5: Click Save template and view your blog. What you can see the title of your blog post has been change to Post Title | Blog Title.
Now you have successful SEO your blog post title.
And more info you can share at comment.