Difference between free and paid themes
Free themes are available to download for everyone on internet without any requirements. Everyone with WordPress install can easily find them on internet or theme store by official site. Premium themes are full of features and a real site can be created with them which is best for everyone. There are 4 different types of free themes available these days.

Build As Free
Few of people created themes free for everyone and all features what ever is built is meant to use without any payments. These are rare themes because only few people create themes free for purpose of helping good people who cant purchase.

Short Versions
Another type of themes are short versions of paid themes. Every one who created a premium theme with complete features mostly provide with free theme including some features. They want people to actually test what its look like to use their premium theme. People can test it with provided few settings and experience what it will look like f they buy premium including full features.

Old Themes
Sometimes its possible that old premium themes are given to people for free use. Owners of these themes already took full advantage by selling them for sometime. Now they have decided to give away free. Another reason is that these themes are out of competition and different sites owners are looking to buy some latest themes and no one is showing any interest to buy them.

Null Themes
Some websites are providing with full premium theme as free which is not legal. These themes are a different versions of originals themes. Its possible there is some kind of dangerous virus in these themes which can become major problem for site owners. Almost all premium themes and free themes are included in those sites for free. Some themes may have no options at all. Many themes are not even working after download. We suggest everyone to stay away from this kind of themes. Its better to use a legal free theme compare to this time of premium themes.

Premium Themes
Its famous business to create a theme for WordPress and sell them on many famous websites. Few popular themes are sold thousands of time already and become good profit for their owners. These themes provides with awesome customization options which are not possible to be seen free. Users can change whatever they want on site from header to footer.

Too many colours and styles are available to choose. We suggest to ignore theses theme until you start earning money from your site. But business owners or those who are looking for using WordPress to sell products must buy a better premium theme.

Too much Customization
People should know what they planning to purchase for site. Most of premium themes are adding too much options which become mess and problem for someone who buy them. These options confuse them with everything. They don’t know how to setup site and may start thinking they waste their money already. We suggest you to ask someone about how this theme look like instead of just purchase it.

Effects of themes on each site
Themes are important part of each website and they are not just front of every site but effect on speed too. Some themes with too much graphics and many options available are slow to surf for everyone. Site owners should choose a better theme which is good for their site.

Speed
Some theme are very low in size but their speed is impressive. One problem with this type theme is that they don’t have much options to choose for customizing site. Most themes are very heavy in size and make our site slow but they have options available to make our site look awesome compare to our competition. We suggest everyone to choose a perfect theme which is light weight and includes good customization options.

Most Downloaded Themes
Another mistake which new site owners or many people may do is run after high downloaded themes. They think that a theme which is downloaded more is best for their site. Most of these themes are popular only because their advertisement is awesome or these are free versions of premium themes. No need to get a theme on top of list but we suggest you to choose a theme which is best for you even its new created. Focus on getting theme which is totally free for everyone.

Style
It depends on your theme how your site look like for visitors. People may not like to visit again if your site look really bad. Don’t add too much options on site and confuse everyone. There is no need to choose color which you love most instead of think about what users required. We suggest you to add your pages with categories on top of site and one sidebar with some other widgets.

Mobile Responsive
One major problem with theme is that some of them are not mobile responsive. Some theme are good for mobile and other are only awesome to work on Pc. This is major effect on site because of themes as most users are only using mobile for normal daily routine tasks.

Use of mobile is too much increased with time. Another option is AMP which create a different site version to work with speed on mobile. We suggest to choose a better theme which work for both mobile and Pc. Use AMP is not good because they provide with few mobile responsive free themes only.

Top Websites to Download Free Themes
One of best source and providing latest awesome theme is WordPress.org which is official site. Over 50 free theme are on Access Press Theme which is great collection of free theme. Athemes provide with list of most popular free themes. Some other famous sites are Theme Forest, Theme Isle, Colorlib and Just Free Themes. Other sites are build to provide free, premium and all type of themes but Just Free Theme is different from them with only free themes.

Short Summary of Best free WordPress Themes of all time
Iconic One
Astra
Ocean WP
GeneratePress
Storefront
Bunny Press Lite
Gridzone
Almighty
Blossom Recipe
News Box Free

https://top10listss.com/best-free-wordpress-themes-of-all-time/