A plugin is a collection of files such as php, css and html, which containes functions and tables that can be implemented to a wordpress website or blog.
It means you can improve the functionality of the website or blog using wordpress plugins. In other words we can say that a plugin is used to add extra features in your website or blog. Such as to create a custom enquiry form, photo gallery, video gallery, advance menus, seo, animated clock etc.
There are lots of free plugins available in wordpress which can be downloaded from wordpress.org. Plugins are also premium or paid WordPress plugins. Paid plugins usually offer a full time support by their developer so if you are using a paid wordpress pluging then you don't have to worry about support and maintenance of the plugin. Paid plugin offer better features as a result.
Wordpress user often look for a paid plugin becuse some free plugin can not fullfill the needs or it may have limited features.
If you are downloading free wordpress plugin, you can install and use the plugin without paying anything. Some advance features can be locked in free plugins. If you want to use them, then you have to pay.
A wordpress plugin can be downloaded from wordpress.org. A lots of free plugins are available in wordpress.org.
WooCommerce is a flexible, open-source eCommerce solution plugin built on WordPress. This plugin is very helpful for small or medium level online store.
It have many features such as
Popup Maker – Popup Forms, Opt-ins & More
Create Effective Popups For WordPress. Popup Maker is the best popup plugin WordPress has to offer. It is incredibly versatile & flexible. Bend it to create any type of popup, modal, or content overlay for your WordPress website.
This plugin is used to help website to rank higher in search engines. Yoast SEO is here to help you related to everything of SEO.
A dedicated and experienced team of developers, testers, architects and SEO experts work daily to improve the plugin.
Yoast SEO have many advance features such as
Social Media Share Buttons & Social Sharing Icons
Social media plugin which let’s you add share icons for RSS, Email, Facebook, Twitter, LinkedIn, Pinterest, Instagram, Youtube etc. This free plugin has many features. Even more can be found in the Premium Plugin.
Some other popular free plugins are
Contact Form by WPForms – Drag & Drop Form Builder for WordPress
WP User Manager – User Profile Builder & Membership
WP Google Maps - To Add Google Maps
Image Gallery etc