Performance Views:

v$sql the details -if you have multiple copies of the query:
"select * from T" in shared pool, v$sql will have a row per query. This can happen if user U1 and user U2 both have a table T and both issue "select * from T". Those are entirely different queries with different plans and so on. v$sql will have 2 rows.

v$sqlarea is a aggregate of v$sql. It selects out DISTINCT sql.
"select * from T" will appear there.

v$sqltext is simply a way to see the entire query.
The v$sql and v$sqlarea views only show the first 1000 bytes. newlines and other control characters are replace with whitespace.

v$sqltext_with_newlines is v$sqltext without the whitespace replacment.