Why do we use the name of body() such as " task body()" inside sequence?

In reply to UVM_LOVE:

“body” was the identifier name chose by the person(s) who wrote that portion of the OVM code. This is reference to the “body” of a task or function, which usually means the procedural statements, or executable implementation of the task/function.

A UVM sequence implements the functor design pattern in SystemVerilog. The sequence object is your pointer and the body() is the function reference.

I just answered your second question in another post.