tikv: refine description of MVCC (#16524)

tidb-storage.md

@@ -74,7 +74,9 @@ As we distribute and replicate data in Regions, we have a distributed Key-Value
 
 ## MVCC
 
-Many databases implement multi-version concurrency control (MVCC), and TiKV is no exception. Imagine the situation where two clients modify the value of a Key at the same time. Without MVCC, the data needs to be locked. In a distributed scenario, it might cause performance and deadlock problems. TiKV's MVCC implementation is achieved by appending a version number to Key. In short, without MVCC, TiKV's data layout can be seen as:
+TiKV supports multi-version concurrency control (MVCC). Consider a scenario where Client A is writing to a key simultaneously as Client B is reading the same key. Without the MVCC mechanism, these read and write operations would be mutually exclusive, posing performance issues and deadlocks in a distributed scenario. However, With MVCC, as long as Client B performs a read operation at a logical time earlier than the Client A write operation, then Client B can correctly read the original value at the same time Client A performs the write operation. Even if the key is modified multiple times by multiple write operations, Client B can still read the old value according to its logical time.
+
+TiKV MVCC is implemented by appending a version number to the key. Without MVCC, the Key-Value pairs of TiKV are as follows:
 
 ```
 Key1 -> Value
@@ -83,7 +85,7 @@ Key2 -> Value
 KeyN -> Value
 ```
 
-With MVCC, the key array of TiKV is like this:
+With MVCC, the Key-Value pairs of TiKV are as follows:
 
 ```
 Key1_Version3 -> Value