docs:update en's background

README.md

@@ -15,6 +15,11 @@
 
 **Home Page: [usthe.com/sureness](https://usthe.com/sureness) or [su.usthe.com](https://su.usthe.com/)**  
 
+## Background   
+
+In the mainstream web architecture, how to protect the restful api provided by the back-end through effective and fast authentication has become particularly important.     
+For existing frameworks, whether it is apache shiro which does not natively support rest, or deeply bound spring, the slower performance and steep learning curve of spring security are not our ideal framework.   
+Ever since sureness was born, we hope to solve these, provide a **restful api**, **no framework dependency**, can **dynamically modify permissions**, **multiple authentication policies**, **faster**, **easy to use and extend** security framework.        
 
 ## <font color="green">`Introduction`</font>
 
@@ -52,7 +57,7 @@
 **In contrast, sureness basically does not consume performance, and the performance (TPS loss) is 3 times that of shiro and 1700 times that of spring security.**      
 **The performance gap will be further widened as the api matching chain increases.**      
 
-Detail see [Benchmark Test](https://github.com/tomsun28/sureness-shiro-spring-security)    
+Detail see [Benchmark Test](https://github.com/tomsun28/sureness-shiro-spring-security-benchmark)       
 
 ##### Framework Sample Support  
 
@@ -173,7 +178,7 @@ Sureness provides the following common interfaces as extension points:
 - `PathTreeProvider`: Resource data provider, it can load data from txt or database,etc.
 - `SurenessAccountProvider`: Account data provider, it can load data from txt or database,etc.   
 
-Refer to [Extension Point](docs/extend-point.md) for the extended documentation.   
+Refer to [Extension Point](https://usthe.com/sureness/#/extend-point) for the extended documentation.   
 
 1. **Custom Subject**
 

docs/extend-point.md

 ## Advanced Use  
 
-If know sureness Process flow, maybe know the extends point.  
-Sureness supports custom subject, custom subjectCreator, custom processor and more.  
-Suggest look these interface before extending:  
+Sureness supports custom subject, custom subjectCreator, custom processor and more.
 
-- `Subject`: Authenticated authorized  user's account interface, provide the account's username,password, request resources, roles, etc.  
-- `SubjectCreate`: Create subject interface, provider create method.    
-- `Processor`: Process subject interface, where happen authentication and authorization.   
-- `PathTreeProvider`: Resource data provider, it can load data from txt or database,etc.  
-- `SurenessAccountProvider`: Account data provider, it can load data from txt or database,etc.     
-
-Sureness process flow:    
+Before advanced custom extension, let's first understand the general process of sureness:
 
 ```mermaid
 graph TD
@@ -18,4 +10,14 @@ A(request in) --> B(s)
 B(subjectCreate creates different key - subjects based on the request header content,every key can be tried once) --> C(s)
 C(Different key authentication methods<differnet lock - processors> to process incoming key - subjects) --> D(s)
 D(Once successful is successful and ends, failure means the next key lock attempt until the end of all attempts)
-```
\ No newline at end of file
+```
+
+As in the above process, Subject is created by SubjectCreate according to the request body, and different authentication processors process the supported Subjects.
+
+Sureness provides the following common interfaces as extension points:
+
+- `Subject`: Authenticated authorized  user's account interface, provide the account's username,password, request resources, roles, etc.  
+- `SubjectCreate`: Create subject interface, provider create method.    
+- `Processor`: Process subject interface, where happen authentication and authorization.   
+- `PathTreeProvider`: Resource data provider, it can load data from txt or database,etc.  
+- `SurenessAccountProvider`: Account data provider, it can load data from txt or database,etc.