Some Useful Dictionary Views For Database Objects In Oracle

select
* from user_objects;
select * from user_tables;
select * from user_tab_cols;
select * from user_constraints;
select * from user_cons_columns;
select * from user_views;
select * from user_sequences;
select * from user_synonyms;
select * from user_tab_comments;
select * from user_col_comments;