kiranminal,
Those are the size of your headings. Search Engines put special emphasis on what you start each of your pages with so you definitely want to include your page's keyword on the H1 heading to start your page.
It is also a good idea to use a couple of h2 or h3 headings further down the page with your keyword or variations of it included in that heading.
For instance on this page maybe something like:
<h2>What Is The Importance Of Headings For SEO?</h2>
Then you may add content below this in the form of paragraphs and possibly bullet points etc. Search Engines pay special attention to headings as they emphasize what your content is focusing on.
Be sure to keep plenty of white space between paragraphs and don't string too many sentences together. 3-5 sentences per paragraph is usually the recommended limit.
As you add more content to the page you may want to add another heading when changing the subject a bit or focusing on something in particular.
Like this:
<h3>Do Headings Help My Visitors Stay At My Site Longer</h3>
Yes headings do help you visitors in many ways. Most website readers scan pages looking for what they searched for at the engines and found your website for to begin with. Many times this is not right at the top of a page.
So making your content stick out with the use of headings and bullets helps your visitors find what they are looking for and keeps your pages from looking too time consuming to find anything.
Gosh, Smith, I could go on and on here. Suffice it to say getting you pages optimized for the search engines and reader friendly right out of the gate will save you a lot of work later editing your content after you get more experienced at website design and general content copy writing skills.
Best wishes,
manasin
I would suggest spending some time educating yourself now, it will pay huge dividends down the road.