If you want to know whether any database links exist in data dictionary views, and where the database links connect to, you can get the information from DBA_DB_LINKS view.
Just launch your SQL*Plus or Toad, or whatever convenient to you and query the dba_db_links table. For example:
SQL> select * from dba_db_links;
And you will be seeing listing of database links defined, with details of OWNER, DB_LINK, USERNAME, HOST, and CREATED, which the column name itself is more or less self-explanatory.
Normally the OWNER of the database link is the person who created it, unless it was created as a public link, in which case a pseudo-user called PUBLIC is said to own it.
Beside, if you define connection host string as an entry (alias) from tnsnames.ora when creating the database links, the HOST column will show the tnsnameas alias, and not the host or remote server name that the database link is connecting to. You have to check tnsnames.ora to get the connection details.