tnslsnr.exe is a process associated with Oracle TNS Listener from Oracle.
Leave this process running if you are running an Oracle database and you want other users to connect to it.
Non-system processes like tnslsnr.exe originate from software you installed on your system. Since most applications store data in your system's registry, it is likely that over time your registry suffers fragmentation and accumulates invalid entries which can affect your PC's performance. It is recommended that you check your registry to identify slowdown issues