It means “Experience of Oneness is true Wisdom”. Full verse:
Abheda Darshanam Jnanam, Dhyanam Nirvishayam Manam;
Snaanam mano mala thyagam, Showcham indriya Nigraham” ||
Meaning: The real Jnana is experiencing Oneness; real Dhyana is controlling the Manas from all temptations. The real snana or Bathing is cleansing of all impurities from mind. Real Showcha or cleanliness is controlling the Indriyas (senses)
The last 3 items are the pre-requisite for Abheda Darshana and it comes from within. The verse is written with English because it is easy to follow. Sankrit is considered language of Devataas (Deva Bhasaa). No English translation will capture the essence fully. The message binds all the components together. It is very instructive, succinct, extremely profound, yet relatively easy to understand.