Question

What is SGA? Can you explain me in a simple manner?

Answer 1

The Oracle documentation does a pretty good job. An excerpt follows:

The SGA comprises a number of memory components, which are pools of
memory used to satisfy a particular class of memory allocation
requests. Examples of memory components include the shared pool (used
to allocate memory for SQL and PL/SQL execution), the java pool (used
for java objects and other java execution memory), and the buffer
cache (used for caching disk blocks).