Basic Concepts

It may help, for your doubt.
1. Create DataBase in wordpress => Name of table Prefix (must) => WP (Ex: WP_tablename)

2. WP default tables total => 11 tables (depend on the version it may increase)

3. Developer also can create a table.Creation of table not an issue. But column name will give (may) the issue when you upgrade the new version of WP. So , again (when you upgrade new version) need to create same table.

4. Remove HTML Tags from content (Ex: posted comment) user following method
$string1 = get_the_content();
$string2 = Strip_tags($string1);

5. If you post comment (after customized wp or Text Editor) from admin panel,
a. test comment => It Update into DB. But It will not display properly in FrontEnd.
b. <em> test comment</em> => it will update into DB. And also it will display correct format from FrontEnd.

6. StripSlashes_deep() ,and esc_attr() function are used for HTML tag purpose
a. Esc_attr() => used for => converting html tag from < (lessthan symbol) => to => <
Before inserting into Database.

7. WordPress text Editor name => TinyMCE (Default, you may change other editor also)

8. Text Editor Cancel and Submit form Button link are coming under following file

Some Usefull Functions or methods :
1. wp_page_menu() -> Return all the menus

2. echo is_front_page(); -> Is home page or not

3. is_home() -> find out home page or not

4. wp_title(); -> Return website title

5. echo get_bloginfo(‘name’); -> Website name

6. echo home_url(); -> Return Url

7. echo $pagename = get_query_var(‘pagename’); -> return page name