What is a Theme?
As per Official WordPress site WordPress theme system is a way to "skin" your weblog. Where Skinning your site implies that only the design is changed. WordPress Themes can provide much more control over the look and presentation of the material on your website.
Basically, a WordPress theme is a collection of files that work together where it produces a graphical interface with an underlying unifying design for a weblog. Now these files are called template files. And in the theme it modifies the way the site is displayed and in the theme it may include customized template files like image files (*.jpg, *.gif), style sheets (*.css), custom Pages, as well as any necessary code files (*.php).
As you know WordPress is an open source database-driven content management system where it allows you to manage content, page, media, create menus etc. In other words WordPress gives you the power to take control of your website without your web administrator's help.
If we change the WordPress theme then the whole layout of your website will change. And you can find the best theme for your website in the WordPress admin area from where you can change, manage or add new themes. If you are planning to use the default WordPress theme then it has a limited number of theme available. So if you want to change your WordPress theme, you’ll find a lot of free one at WordPress.org Themes Directory.
You no need to worry about the security because they are taken care with good security measures in regards to SEO to know beforehand if your WordPress theme is well SEO optimized and all the new coding rules are applied in the right manner. On the other hand if your theme is using too many resources like HTTPs request to your server for a various reason or if it is just badly coded then all these factors will affect your SEO and also your website performance.
How can I create my website with WordPress?
One the best part why more and more people are using the WordPress is that to make/create a website you no need to have technical knowledge. All you need to do is select a web hosting plan. Because most of the hosting company will provide pre-installed WordPress for your when you choose their hosting plan.
So once the sign up for a hosting plan next you can simply pick a WordPress theme like Customizr Pro, and start designing your website. Now your WordPress is really easy to use and you'll be quickly able to build pages.
How much does it cost?
Since WordPress is an open source CMS it is for free of cost and you no need to pay anything to use it and it is licensed under the GPLv2.
But to use it you need to buy a domain name and also a web hosting plan or your own server. And subscribing to a hosting plan which will cost you a few dollars or Rupees per month for a basic plan, which is usually enough to start hosting a website. Once after installing the WordPress you will be able to choose a free theme for the theme panel. So once after testing them most of the WordPress users purchase a premium theme which generally offers a better design and more customization features than the free ones.
Do I need to be or have a developer to use WordPress?
Nope, not at all! If you are using WordPress then you won't require any particular technical skills to create your website. It is very simple to use and yes it will take a few hours to become 100% familiar with the interface and various possibilities offered by the software.