Positive ions usually form from losing electrons and are called cations.
Explanation
An atom can lose one or more valence electrons and it may also gain one or more valence electrons leading to the formation of ions.
They are electrically charged particles unlike atoms which are neutrally charged.
The atoms can be converted to positive ion on removal of electrons from the valence shell.
Similarly the atoms can also be converted to negative ions when extra electrons get added in the valence shell.
So the losing of electrons leads to the formation of positive ions which are termed as cation while the gaining of electrons will form negative ions which are termed as anions.